GeoMap area - CGEN Archive · Belcarra Belcarra ort Moody ancouver Langley City Abbotsford BURRARD...
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Map based on R. Kreye and M. Wei, 1994, A proposed aquifer classification system for groundwater management in British Columbia, British Columbia Ministry of Environment, Lands, and Parks, Water Management Division, Hydrology Branch, Groundwater Section, 67 p. landslide Slopes and Landslides 0 20 kilometres The slope of the land surface ranges from nearly horizontal on floodplains to more than 20 through much of the Coast and Cascade Mountains and on escarpments bordering uplands in the Fraser Valley. Why is slope important? First, it affects surface drainage -- in a general sense, drainage improves as the land surface steepens. Second, slope is an important factor in the stability of the land surface -- most landslides in the Vancouver area occur on slopes that are steeper than 20 (red areas on this map). Locations of many of the landslides that have occurred in this century in the Fraser Valley are plotted on the map (landslides in the Coast and Cascade Mountains are not included). Most landslides in the Fraser Valley involve Ice Age sediments and are triggered by intense rainstorms. In contrast, many of the landslides in the Coast and Cascade Mountains are in bedrock ( and ). A common type of landslide in both regions is rapid flows of water-saturated debris ( ). o o rockfalls rockslides debris flows Locations of landslides from Armstrong and Hicock 1979, 1980 (see ADDITIONAL INFORMATION) and G.H. Eisbacher and J.J. Clague, 1981, Urban landslides in the vicinity of Vancouver, British Columbia, with special reference to the December 1979 rainstorm, Canadian Geotechnical Journal, v.18, pp. 205-216. Slope data derived from British Columbia government Terrain Resource Information Management (TRIM) data. Steveston Ladner Tsawwassen Pitt Meadows White Rock Cloverdale Brookswood Haney Barnston Island Fort Langley Aldergrove Matsqui Mission Huntington Vedder Crossing Rosedale Agassiz Ferry Terminal Deltaport Westham Island Vancouver International Airport Queen Elizabeth Park Iona Island Causeway Burns Bog Lulu Island Annacis I Kitsilano Jericho Beach Point Grey Capitol Hill Mount Burnaby Stanley Park Sentinel Hill Pitt Polder Hatzic Prairie Columbia Valley Mount Vedder Sumas Prairie Sumas Mountain Matsqui Prairie Chilliwack Mountain Grant Hill F R A S E R R I V E R R I V E R 1 99 West Vancouver North Vancouver Burnaby New Westminster Richmond Surrey Chilliwack Coquitlam Port Coquitlam Belcarra Belcarra Port Moody Vancouver Langley City Abbotsford BURRARD INLET ENGLISH BAY S e c o n d N a r r o w s F i r s t N a r r o w s MUD BA Y PITT RIVER Stave Lake Hayward Lake Hatzic Lake N i c o m e n S l o u g h River Harrison F R A S E R Cultus Lake BOUNDAR Y BA Y S e r p e n t i n e R i v e r R i v e r N i c o m e k l Vedder Canal C h i l l i w a c k R i v e r River River C o q u i t l a m S e y m o u r L y n n C r e e k R i v e r C a p i l a n o R i v e r A l o u e t t e 0 2 4 6 8 10 Kilometres CANA D A UNITED STATES OF AMERICA BRITISH C OL U MBIA WASHINGTON for description of geologic units on this map, see illustrated map legend and colour key on panels to left Legend Shaded relief topographic map derived from British Columbia government Terrain Resource Information Management (TRIM) data. Geological units based on previous mapping cited in ADDITIONAL INFORMA TION. for description of geologic units on this map, see illustrated map legend and colour key on panels to left Legend Shaded relief topographic map derived from British Columbia government Terrain Resource Information Management (TRIM) data. Geological units based on previous mapping cited in ADDITIONAL INFORMA TION. Transverse Mercator Projection (Central Meridian 122°30' W) North American Datum 1927 Ten Thousand Metre Universal Transverse Mercator Grid Zone 10 0 20 kilometres Moderate to High (modern lowland sediments) Low - except adjacent to small streams (uplands and mountains) 1 Flood Hazard This map provides a generalized interpretation of hazard based on the distribution of modern flood deposits. Low-lying areas adjacent to rivers and the sea shore are coloured red. These areas are underlain by modern flood and coastal storm deposits. The red zone includes of the Fraser River and its tributaries, and gently sloping fans at the mouths of the Chilliwack, Coquitlam, Seymour , Capilano rivers. This zone also includes poorly drained areas in the Nicomekl and Serpentine river valleys. Although most of these areas have been dyked to protect people and property , they are still at risk from rare, exceptionally large river floods. Low-lying shorelines exposed to waves and strong winds can also be flooded during exceptional storms if the winds push water inland. Localized flooding can occur at the front of the Fraser delta when a storm or high tide coincides with a Fraser River flood. In both the red and grey zones on the map, small streams, which are not shown at this scale, can also overflow their banks. These relatively small floods are triggered by heavy rainstorms. floodplains For more detailed information on flood hazard contact the responsible municipal or regional government or the British.Columbia Ministry of Environment, Lands and Parks, W ater Management Division. Earthquak e Liquefaction Lowland (modern sediments) Mountains (bedrock) Uplands (Ice age sediments) Moderate to High (modern lowland sediments) Low (Ice Age upland sediments) Nil (bedrock) 0 20 kilometres 1 1 Vancouver Richmond Surrey Langley Strait of Georgia Fraser River Abbotsford Mission White Rock Sumas Prairie Chilliwack Physiography of GeoMap 0 20 kilometres A A’ B B’ Boundary Bay 0 20 kilometres high vulnerability heavy use moderate to high vulnerability low to moderate use Aquifers in Sediment low vulnerability low to heavy use < 10 10 - 20 Slope Angle > 20 high vulnerability Aquifers in Bedrock Aquifers not asse ssed 1 Cascade Mountains Earthquak e Ground Motion Canada USA USA Canada Pacific Ocean British Columbia 0 400 kilometres Seismic zones increasing seismic hazard Ground motion, the definitive characteristic of earthquakes, causes damage directly by vibration and indirectly through secondar y effects such as landslides and liquefaction. Structural design in earthquake-prone areas such as southwestern British Columbia is based on anticipated peak horizontal ground acceleration and velocity values provided by the Geological Survey of Canada. These parameters are derived from statistical analysis of past earthquakes and require an understanding of the causes of earthquakes in various regions and estimates of ground motion attenuation relationships (how quickly shaking decreases with distance from an earthquake). This information is incorporated into the National Building Code of Canada in the form of seismic zoning maps. The map to the left shows seismic zones in British Columbia. The zones are based on levels of peak horizontal acceleration with a 10% probability of being exceeded over a 50-year period. This acceleration zoning map is centred near 5 Hertz (5 oscillations per second) - a frequency of ground motion that can damage small or rigid structures. A similar zoning map (not shown) in the National Building Code for peak seismic velocity is centred near 1 Hertz, a frequency that can damage larger structures (e.g. 10-storey buildings). Engineers use this information to design earthquake-resistant structures. These maps represent the intensity of shaking on rock. Local geology and topography may amplify ground shaking at some frequencies and may de-amplify shaking at other frequencies. There is no map yet for Vancouver and the Fraser Valley showing areas of expected ground amplification or de- amplification. The map shown here does not include possible effects of rare, very large, subduction-type earthquakes west of Vancouver Island; shaking produced by these earthquakes will be considered in the next generation of seismic zoning maps. Map based on P.W. Basham, D.H. Weichert, F.M. Anglin, and M.J. Berry, 1982, New probabilistic strong seismic ground motion maps of Canada: a compilation of earthquake source zones, methods and results, Geological Survey of Canada, Earth Physics Branch Open File 82-33, 202 pp. GeoMap V ancouver Geological Map of the V ancouver Metropolitan Area Geological Survey of Canada Open File 3511, 1998 Robert J.W . Turner and John J. Clague; Bertrand J. Groulx, J. Murray Journeay Bertrand J. Groulx Robert Cocking, Andrew Makepeace, Kazuharu Shimamura, Sonia T alwar Design and cartography : Digital cartography by the GSC P acific GIS group: GeoMap V ancouver is available from: Geological Survey of Canada Sales and Publications 101 - 605 Robson St. Vancouver , B.C. V6B 5J3 Tel. (604) 666-0271 F ax. (604) 666-1337 email address: [email protected] website: www .nrcan.gc.ca/gsc/ Helpful reviews of draft versions of GeoMap Vancouver were provided by John Cassidy, Sandy Colvine, Ron DiLabio, Julian Dunster, Kathy Dunster, John Gartner, Bob Gerath, Susan Heming, Cathie Hickson, Steve Kellas, Nancy Knight, Rosemary Knight, Jack Mollard, Peter Mustard, Jim Roddick, and Alan Whitehead. Bev V anlier provided editorial assistance. This map is based on the following Geological Survey of Canada bedrock and surficial geology maps: Armstrong, J.E. and Hicock, S.R. . Map 1484A (1980). . Map 1486A (1979). Amstrong, J.E. . Map 1487A (1980). . Map 1485A (1980). Journeay, J.M. and Monger , J.W.H. . 1:50,000-scale map, Open File 2490 (1995). Roddick, J.A. . Map 1151A (1965). . Map 1152A, (1965). . Map 1153A, (1965). Armstrong, J.E. 1990. . Geological Association of Canada, Cordilleran Section, V ancouver, B.C. Armstrong, J.E. 1984. . Geological Survey of Canada Paper 83-23. Clague, J.J. 1996. . Geological Survey of Canada Bulletin 494. Halstead, E.C. 1986. . Environment Canada, National Hydrology Research Institute (NHRI) Paper No. 26. Monger, J.W.H., 1994. Geological Survey of Canada, Bulletin 481. Turner, R.J.W., Clague, J.J., and Groulx, B.J. 1996. Geological Survey of Canada Open File 3309, poster . Surficial geology , New Westminister, British Columbia Surficial geology , Vancouver, British Columbia Surficial geology , Chilliwack (west half), British Columbia Surficial geology , Mission, British Columbia Geology and crustal structure of the southern Coast and Intermontane belts, southern Canadian Cordillera, British Columbia Geology, Pitt Lake (V ancouver , east half), British Columbia Geology, Vancouver North, British Columbia Geology, Coquitlam, British Columbia Vancouver geology Environmental and engineering applications of the surficial geology of the Fraser Lowland, British Columbia Paleoseismology and seismic hazards, southwestern British Columbia Ground water supply -- Fraser Lowland, British Columbia Geology and geological hazards of the V ancouver region, southwestern British Columbia. Geoscape V ancouver -- living with our geological landscape. Other publications on geology , geological hazards, and groundwater of the Vancouver metropolitan area: ADDITIONAL INFORMATION 1 km 2 km surface 1 km 2 km surface 1 km 2 km surface A A’ B B’ Vertical exaggeration of 5 times in subsurface Water Older bedrock (granitic, volcanic, sedimentar y) Sandstone bedrock Fault (with direction of movement) Ice Age sediments Modern sediments Surface Subsurface projection of fault to sur face Beneath V ancouver see map at left for location of sections A-A ', B-B' This three-dimensional perspective view illustrates the subsurface geology of Vancouver and the Fraser Valley. Knowledge of geology at depth comes from drill holes and geophysical surveys. Because this information is limited, the interpretation shown here is speculative. The diagram shows a deep basin in beneath the Fraser Valley. filling this basin is more than 4 km thick near Tsawwassen but pinches out at the edges of the basin. The sandstone, in turn, is overlain by Ice Age sediments up to 1 km thick. Generally thinner modern sediments are limited to low- lying areas (Fraser delta) and the Strait of Georgia, where they are currently being deposited. (fractures along which there has been movement) offset bedrock and control some linear features such as Sumas Prairie. These faults are not known to be active. granitic rock Sandstone Faults Sumas Mtn. Chilliwack Vedder Mtn. Fraser River Stave Lake Abbotsford Huntington Tsawwassen Sumas Prairie Delta Delta Boundar y Bay Fraser River Downtown Vancouver Horseshoe Bay Howe Sound Richmond B B’ A A’ GeoMap area 0 20 kilometres Squamish Vancouver Richmond Pitt Lake I n d i a n Ar m Stave Lake Surrey Langley Bellingham Boundary Bay Fraser River Abbotsford Mission White Rock Sumas Prairie Chilliwack Hope Fraser Canyon Mt. Baker Cascade Mtns Chuck anut Hills Howe Sound Harrison Lake Strait of Georgia N o o k s a c k R i v e r CANAD A U.S.A. Coast Mtns Coast Mtns Fraser V alley British Columbia GeoMap area GeoMap F rom Space The Fraser Valley is a triangular -shaped lowland bordered by the Coast Mountains, and the Cascade Mountains and Chuckanut Hills. The Fraser River, draining a vast interior basin, breaks through the coastal mountains to reach the Strait of Georgia. includes that portion of the Fraser Valley lying on the Canadian side of the International Boundar y. GeoMap Vancouver Geological Map of the V ancouver Metropolitan Area Geological Survey of Canada Open File 3511, 1998 Ressources naturelles Canada Natural Resources Canada 1 8 4 2 C A N A D A G E O L O G I C A L S U R V E Y - C O M M I S S I O N G E O L O G I Q U E This map provides only a generalized interpretation of liquefaction susceptibility during an earthquake and should not be used for local geotechnical evaluation. Brookswood aquifer Abbotsford aquifer During an earthquake loose water-saturated silts and sands at shallow depth may lose their strength and transform into a fluid ( ). Deeper sediments are more consolidated, have higher confining pressures, and consequently are less likely to liquefy. When sand beneath a layer of silt or clay liquefies, the capping layer may "glide" laterally under the influence of gravity towards a slope, such as the bank of a nearby river channel, causing ground cracking. Foundations of highways, bridges, and buildings, as well as buried sewer and gas lines, can be damaged by such movements. Liquefaction can also trigger landslides at the front of the Fraser delta. The red zone shows areas of relatively loose, saturated lowland sediments (i.e. lowlands). Liquefaction is likely to occur during a strong earthquake in those parts of the red zone where there is shallow subsurface sand and coarse silt, for example the Fraser delta. liquefaction Physiography Mountain uplands lowlands is the surface form of the Earth. The Vancouver region includes three main physiographic areas. areas (Coast and Cascade Mountains) comprise rugged bedrock ridges and peaks and intervening steep- walled valleys. The larger valleys contain thick modern and Ice Age sediments and also host large lakes and streams. The other two physiographic areas are within the Fraser Valley. Higher parts of the Fraser Valley are gently rolling , ranging from about 15 m to 250 m above sea level. Uplands are underlain by thick Ice Age sediments, largely of glacial origin. Flat occur along the Fraser River and its tributaries and are underlain by modern sediments. Aquifers are bodies of sediment or rock that are saturated and sufficiently permeable to provide subsurface water to wells. Most groundwater in the Fraser Valley is derived from aquifers in modern and Ice Age sediments. These aquifers are a major source of high-quality water for drinking and other uses. The British Columbia Ministry of Environment, Lands and Parks has classified 71 aquifers in the Fraser Valley according to current levels of use and vulnerability to contamination. Almost two-thirds of the aquifers are shallow and can be easily contaminated by downward infiltration of waters laced with agricultural fertilizers and pesticides, manure, septic effluent, or gas and oil from leaking storage tanks. The most heavily utilized of these highly vulnerable aquifers occur in the Abbotsford and Langley/Brookswood areas. Less developed, but highly vulnerable aquifers occur in sediments below the floodplain and delta of the Fraser River. Deeper aquifers overlain by silts, clays, or tills of low permeability are less vulnerable to contamination. The most important of these deep aquifers occur in the Aldergrove area; others underlie the uplands of Vancouver , Burnaby , Surrey, and Langley , and the lowland of the Nicomekl and Serpentine rivers. Some groundwater is also pumped from fractured bedrock, for example, at Grant Hill, Mission, and Belcarra. The thin soil cover over these bedrock aquifers makes them highly vulnerable to contamination. Some aquifers, in both sediments and bedrock, have poor water quality due to elevated levels of naturally occurring substances such as chloride, iron, sulphur, and fluoride. Geo Map : Earth (from Greek - Earth); as in geology , the science of the solid Earth : A visual display of spatial data geo GeoMap Vancouver is a geological map of the Vancouver metropolitan area. This area is underlain by diverse geological materials with different physical properties. The purpose of GeoMap Vancouver is to show the surface distribution of these materials and to summarize material characteristics that are relevant to engineering, the environment, and land-use planning. Such characteristics include bearing capacity for structures, landslide potential, liquefaction susceptibility , drainage, flood hazard, and contained resources such as groundwater , aggregate, and building stone. The legend and central map show the nature and distribution of the different geological materials. The smaller thematic maps focus on particular attributes and hazards. Panorama looking southeast over the North Shore, V ancouver city , and the Lower Fraser V alley. The Cascade Mtns and Mt. Baker form the skyline and southern margin of the Fraser V alley. B. J. Groulx Groundwater and Aquifers Granitic rock Granitic rocks are a family of medium- to coarse-grained igneous rocks ( ). Granitic rocks in the map area range from 165 to 95 million years old. Where not extensively fractured and faulted, granitic rock is resistant to erosion and can form steep mountain slopes. Granitic rock is locally quarried for use as building stone and crushed rock (Pitt River). granite, granodiorite, quartz diorite, diorite They consist of interlocking light-coloured grains of and , and dark-coloured and , which give the rock a distinctive "salt-and-pepper" texture. feldspar quartz biotite hornblende 1 cm Stawamus Chief near Squamish T. Turner Close-up view of granitic rock J.J. Clague Volcanic rock Dark, fine grained volcanic rocks, chiefly and , are exposed at the northern edge of the Fraser Valley. These rocks formed as lavas, shallow intrusions, and volcanic ash deposits. Most volcanic rocks are resistant to erosion and form prominent hills in the Fraser Valley (Sentinel Hill, Queen Elizabeth Park, Grant Hill). Young volcanic rocks (35-17 million years old) occur as thick tabular , parallel to the layers in the rocks into which they were injected (Grant Hill) and as smaller subvertical that cut across rock layering (Prospect Point, Stanley Park). Much older ( volcanic rocks are exposed on Sumas Mountain and near the confluence of the Harrison and Fraser rivers. basalt andesite sills dykes 185 million years) Queen Elizabeth Park -- an old basalt quarry turned into a garden J.J. Clague Basalt with columnar jointing, near Whistler J.J. Clague Gravel and sand Deposits of gravel and sand occur along steep-gradient streams in mountain valleys (Chilliwack Valley), on alluvial fans and marine deltas at valley mouths (Capilano and Seymour rivers, North Vancouver), and on islands and bars of the Fraser River upstream of Mission. G also occur as beach deposits (Jericho, White Rock) and as debris cones and fans at the base of mountain slopes. Most areas mapped as are at risk of flooding and have a moderate to high liquefaction potential. deposits are (they transmit water), and are thus important shallow . They are also potential sources of aggregate, but shallow water tables limit their use for this purpose. ravel and sand gravel and sand Gravel and sand permeable aquifers Landfill Landfill is material deposited by humans. Fill materials have been dumped in shallow waters and on tidal flats and other wetlands to extend the area of useable land. Recent recognition of the ecological importance of areas destroyed by this practice has led to limitations on placements of fills. Landfill in the Vancouver area is found mainly along shorelines, both marine (False Creek and Burrard Inlet) and river (Annacis Island). It is heterogeneous and includes sand and gravel, till, and/or crushed rock. Landfill also includes waste materials disposed of in municipal dumps (Burns Bog in Delta, Port Mann landfill); these dumps can contribute leachates to local surface and groundwaters and therefore require containment systems. Poorly designed and compacted landfills can be problematic for foundations, and could liquefy and settle during a strong earthquake. Peat Peat is partly decomposed plant material found below bogs, swamps, and marshes. Peat up t o 5 m thick covers much of the Fraser delta east of Highway 99 and the Nicomekl-Serpentine lowland. It also occurs locally on the Fraser River floodplain between New Westminster and Mission, at the base of some upland escarpments, at mountain fronts, and within poorly drained depressions in upland areas. Several bogs (e.g. Pitt Meadows bog, Burns Bog) have been mined for sphagnum peat moss, and the peatlands on the Fraser delta are important producers of blueberries and cranberries. Because of their high compressibility , peats are extremely poor foundation materials. Recognition of the ecological importance of bogs has led to increased efforts to protect them from development. Silt and clay Silt, clay, and loam (mixed clay, silt, and sand) are common on the Fraser River floodplain below Mission, the Pitt River floodplain (Pitt Polder), the Fraser delta, and the Nicomekl-Serpentine flats. These sediments were deposited over thousands of years by seasonal floodwaters that spread across these lowlands. Silt and clay beneath the Nicomekl-Serpentine flats are ancient marine deposits. They were formed by the slow settling of fine river-borne sediment onto the sea floor. These fine-grained sediments make poor foundation materials because of their low bearing capacity , but are generally not prone to liquefaction. They are important agricultural soils, although poor drainage can be a problem. Sand and silt Interlayered sand, silt, and loam underlie parts of Sumas Prairie, the Fraser River floodplain downstream of Mission, and the Fraser delta. Similar sediments also occur along some small streams. The unit, like the aforementioned unit, was deposited during floods. Construction of dykes has greatly reduced such flooding and interrupted the natural deposition of these materials. Sand and silt are important agricultural soils and can be important shallow groundwater reservoirs ( ). Sand-rich deposits have moderate to high bearing capacity and are good foundation materials, but could liquefy during a strong earthquake. sand and silt silt and clay aquifers Modern Sediments in Lowlands About half of the Fraser Valley is flat, flood-prone land below 15 m elevation (mainly the of the Fraser River and its tributaries). This area is underlain by loose, water-saturated sediments that are less than 10,000 years old (i.e. age). Fraser River floodplain sediments consist mainly of gravel and sand from Hope to Mission; sand and silt dominate farther downstream. The Nicomekl-Serpentine and Pitt River valleys and Sumas Prairie are underlain by sand and silt. Poorly drained areas of floodplain are mantled by peat, and landfill has locally extended shorelines. Floodplains contain rich agricultural soils, but are generally poorly drained due to the flat terrain and shallow water table. Although still predominantly rural, some lowlands are areas of rapid urban growth (Richmond). Most communities on floodplains are protected by dykes from all but the largest floods. floodplains Holocene 1m 1m Sand landfill along False Creek J.J. Clague Port Mann landfill R. Turner Mined peat area, Burns Bog, Fraser delta J.J. Clague Peat layers exposed in excavation J.J. Clague Tidal mud, Serpentine River estuary A.C. Clague Modern clayey silt, Serpentine River estuary A.C. Clague Locarno Beach J.J. Clague Beach sand J.J. Clague River bar , Capilano River R. Turner River gravel R. Turner Ice Age Sediments in Uplands Ice Age sediments deposited during the (2 million to 11,000 years ago) underlie gently rolling uplands (15 to 250 m elevation) of the Fraser Valley. Most Ice Age sediments in the Vancouver area date to the last glaciation, about 25,000 to 11,000 years ago, and in particular to the period of glacier retreat when areas below 200 m elevation were covered by the sea. These sediments include deposited directly by glaciers, gravel and sand laid down by streams flowing off the melting ice ( ), marine clay and silt, and beach gravel and sand. Deposits older than the last glaciation are only exposed in steep escarpments along the margins of uplands. Most cities and towns in this region were built on the uplands to avoid the flood and drainage problems of lowland areas. Upland sediments are good foundation materials and are generally not susceptible to liquefaction. Soils developed on gravel and sand are well drained, whereas those developed on silt, clay, and some till deposits are poorly drained. Flooding is limited to the narrow valley bottoms of small streams incising the uplands. Pleistocene Epoch till outwash Silt and clay Thick silt and clay of marine origin are the most widespread surface sediments in the Surrey, White Rock, and Langley-Aldergrove uplands. This unit includes massive and bedded sediments with variable bearing capacities, depending partly on whether or not they were overridden and loaded by glaciers. In general, deposits east of Aldergrove have been loaded by ice and thus have higher bearing strengths. Water infiltration is poor because the sediments are fine grained; this can result in poor surface drainage if the land is flat. Silt and clay deposits on steep slopes (>20 ) are prone to landsliding. Silt and clay deposits exposed during construction activities erode easily and can be a major source of stream siltation. o Sand Scattered sand deposits up to 5 m thick occur on the Vancouver , Tsawwassen, White Rock, and Surrey uplands; they are absent from uplands east of Langley . The sands are beach deposits that formed when uplands emerged from the sea at the end of the last glaciation. They have good bearing strength, but are generally too thin to affect foundations. Water passes through sands with ease, thus soils developed on these materials are well drained. Gravel and sand Deposits of gravel and sand up to 40 m thick are widespread on uplands between Langley and Abbotsford, and north of the Fraser River between Pitt Meadows and Mission. Important deposits also occur on the North Shore, adjacent to the Capilano, Seymour , and Coquitlam rivers, and in the Columbia Valley south of Cultus Lake. Gravel and sand have high bearing capacity and excellent drainage. Thick gravel and sand deposits are important sources of aggregate; there are numerous gravel pits south and east of Aldergrove, and south of Langley. Gravel and sand are also important (the Abbotsford and Brookswood aquifers). Shallow aquifers are vulnerable to contamination from agricultural and industrial activities. aquifers Till Till is a heterogeneous glacial deposit consisting of clay, silt, sand, and stones ranging from pebble to boulder size. Till up to 25 m thick is the dominant surface and near-surface material over much of the Vancouver upland, where it is overlain by patchy marine silt and sand. Farther east, till is an important, but less extensive surface material; it is buried by thick silt and clay in the Surrey and Aldergrove areas. The lower slopes of the Coast Mountains are mantled by up to several metres of till. Some tills are compact and concrete-like, whereas others are sandy and loose. Till commonly has a high bearing capacity and thus is an excellent foundation material. Compact till is nearly impervious; for good drainage, the surface must slope. Silt- and clay-bearing tills disturbed during construction activities can be a major source of stream siltation. Steepland sediments Steep escarpments occur locally at the borders of uplands. Escarpments expose Ice Age sediments that, elsewhere on the uplands, are covered by younger sediments, discussed above. These older sediments include clay, silt, sand, gravel, and . The bases of some escarpments are being actively undercut by ocean waves (Tsawwassen, White Rock, Point Grey) or streams (Chilliwack, Capilano, Seymour , and Coquitlam rivers), making them vulnerable to landsliding. Many residential areas extend to the edges and bases of escarpments; even small slides in these localities can damage or destroy houses, roads, and other structures. till 20 cm 0.5 m 20 cm Blocky weathering, massive marine clay J.J. Clague Layered silt and clay J.J. Clague Layered sand deposited in an ancient lake J.J. Clague Close-up of layered sand J.J. Clague Gravel pit, Aldergrove J.J. Clague Glacial gravel P.T. Bobrowsky Ridges of till at snout of Coast Mountain glacier J.J. Clague Compact till J.J. Clague Buildings near unstable clif f of Ice Age sand and silt, U.B.C. University of B.C. Residences along a steep coastal bluf f, Tsawwassen J.J. Clague Bedrock in Mountains Solid bedrock forms the Coast and Cascade Mountains, as well as smaller mountains that protrude through thick sediments in the Fraser Valley (Burnaby Mountain, Grant Hill, Sumas Mountain, Chilliwack Mountain). Bedrock is commonly mantled by several metres of till, sandy gravel, or rock fragments; less than 10% of the mountain area is actually exposed rock. Bedrock in this region can be grouped into four main units described below. Landslides occur where weak rocks are exposed on steep slopes. Rock weakness can stem from the presence of faults, fractures, sedimentar y layers, or platy mineral layers ( ) that dip in the direction of the slope. Thin sediments overlying bedrock can slide into stream channels during rainstorms, triggering flows of sediment, water, and plant debris ( ) that move downstream at high velocity. foliation debris flows Sandstone Sandstone, siltstone, and conglomerate (85-37 million years old) occur as scattered outcrops in Vancouver , Burnaby , and on the North Shore (Stanley Park, Kitsilano, Burnaby Mountain, Capilano River). These rocks also occur at depth through much of the Fraser Valley. Sandstone layers resistant to erosion and tilted down to the south form ridges with steep north-facing bluffs and gentler south-facing slopes (Burnaby Mountain, Stanley Park). Ridges are separated by valleys eroded into softer siltstone (First Narrows, Burrard Inlet). These rocks are weakly cemented and can be excavated without blasting. About 5-15% of the rock is open pore space making deeply buried sandstones potential natural gas reservoirs. 2 cm Polished slab of sandstone J.J. Clague Layered sandstone and siltstone, Sumas Mountain P.S. Mustard Foliated sedimentary and volcanic rock Metamorphosed sedimentar y and volcanic rocks occur widely in the Cascade Mountains, and also form small hills in the eastern Fraser Valley (Chilliwack Mountain). These rocks are characterized by a planar fabric ( ) formed during burial, deformation, and metamorphism of the rock. This fabric reduces rock strength, causing some rock types to weather into thin platy fragments. Bedrock exposed on Vedder Mountain and east of Cultus Lake is made up of thinly layered, dark , and lesser , , , and . Volcanic rock with interlayers of limestone, argillite, and sandstone is exposed on mountain slopes in the upper Chilliwack River basin. foliation argillite phyllite gneiss limestone chert 20 cm Folds in interlayered sandstone and argillite J.M. Journeay Platy weathering of strongly foliated phyllite J.J. Clague 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Transcript of GeoMap area - CGEN Archive · Belcarra Belcarra ort Moody ancouver Langley City Abbotsford BURRARD...
Map based on R. Kreye and M. Wei, 1994, A proposed aquifer classification system for groundwater management in British Columbia,British Columbia Ministry of Environment, Lands, and Parks, Water Management Division, Hydrology Branch, Groundwater Section, 67 p.
landslide
Slopes and Landslides
0 20kilometres
The slope of the land surface ranges from nearly horizontal on floodplainsto more than 20 through much of the Coast and Cascade Mountains andon escarpments bordering uplands in the Fraser Valley. Why is slopeimportant? First, it affects surface drainage -- in a general sense,drainage improves as the land surface steepens. Second, slope is animportant factor in the stability of the land surface -- most landslides inthe Vancouver area occur on slopes that are steeper than 20 (red areas onthis map). Locations of many of the landslides that have occurred in thiscentury in the Fraser Valley are plotted on the map (landslides in the Coastand Cascade Mountains are not included). Most landslides in the FraserValley involve Ice Age sediments and are triggered by intense rainstorms.In contrast, many of the landslides in the Coast and Cascade Mountainsare in bedrock ( and ). A common type of landslide inboth regions is rapid flows of water-saturated debris ( ).
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rockfalls rockslides
debris flows
Locations of landslides from Armstrong and Hicock 1979, 1980 (see ADDITIONAL INFORMATION) and G.H. Eisbacher and J.J. Clague, 1981,Urban landslides in the vicinity of Vancouver, British Columbia, with special reference to the December 1979 rainstorm, Canadian GeotechnicalJournal, v.18, pp. 205-216. Slope data derived from British Columbia government Terrain Resource Information Management (TRIM) data.
Steveston
Ladner
Tsawwassen
Pitt Meadows
White Rock
Cloverdale
Brookswood
Haney
Barnston
Island
Fort Langley
Aldergrove
Matsqui
Mission
Huntington
Vedder
Crossing
Rosedale
Agassiz
Ferry
Terminal
Deltaport
Westham
Island
Vancouver
International
Airport
QueenElizabethPark
Iona IslandCauseway
B u r n s
B o g
L u l u I s l a n d
Annacis I
Kitsilano
JerichoBeachPoint Grey
Capitol HillMount
Burnaby
Stanley
Park
SentinelHill
P i t t Po lde r
Hatzic
Prairie
Co lu
mb ia
Va l ley
Moun t
Vedder
Su
ma
s
Pr a
i ri e
Sumas
Mountain
Matsqui Prairie
Chilliwack
Mountain
Grant Hill
FR
AS
ER
RI
VE
R
R I V E R
1
9 9
West Vancouver
North Vancouver
Burnaby
New
Westminster
Richmond Surrey
Chilliwack
Coquitlam
Port Coquitlam
Belcarra
Belcarra
PortMoody
Vancouver
Langley
City
Abbotsford
B U R R A R D I N L E T
E N G L I S H
B A Y
S e c o n d N a r r o w s
F i r s tN
arro
ws
M U D B A Y
PI
TT
R I V E R
S t a v e
L a k e
Ha
yw
ar d
La
ke
H a t z i c
L a k e
N i c o me
n
S l ou
g
h
R i v e r
Ha r r i s o n
FR
AS
ER
C u l t u s
L a k e
B O U N D A R Y B A Y
Se r p e n t i n e
R i v e r
Ri v
er
N i c o m e k l
Ve
dd
er
Ca
na
l
C h i l l i w a c k
R i v e r
R i v e r
Ri
ve
r
Co
qu
it
la
m
Se
ym
ou
r
Ly
nn
Cr
ee
k
Ri
ve
r
C a pi l a
no
Ri
ve
r
Al o
u
ette
0 2 4 6 8 10
K i l o m e t r e s
C A N A D A
U N I T E D S T A T E S O F A M E R I C AB R I T I S H C O L U M B I A
W A S H I N G T O N
for description of geologic units on this map, seeillustrated map legend and colour key on panels to left
Legend
Shaded relief topographic map derived fromBritish Columbia government Terrain ResourceInformation Management (TRIM) data.
Geological units based on previous mappingcited in ADDITIONAL INFORMATION.
for description of geologic units on this map, seeillustrated map legend and colour key on panels to left
Legend
Shaded relief topographic map derived fromBritish Columbia government Terrain ResourceInformation Management (TRIM) data.
Geological units based on previous mappingcited in ADDITIONAL INFORMATION.
Transverse Mercator Projection(Central Meridian 122°30' W)North American Datum 1927
Ten Thousand MetreUniversal Transverse Mercator Grid
Zone 10
0 20kilometresModerate to High(modern lowland sediments)
Low - except adjacent to small streams
(uplands and mountains)
1
Flood HazardThis map provides a generalized interpretation of hazard based on the distribution of modern flooddeposits. Low-lying areas adjacent to rivers and the sea shore are coloured red. These areas are underlainby modern flood and coastal storm deposits. The red zone includes of the Fraser River and itstributaries, and gently sloping fans at the mouths of the Chilliwack, Coquitlam, Seymour, Capilano rivers.This zone also includes poorly drained areas in the Nicomekl and Serpentine river valleys. Although mostof these areas have been dyked to protect people and property, they are still at risk from rare, exceptionallylarge river floods. Low-lying shorelines exposed to waves and strong winds can also be flooded duringexceptional storms if the winds push water inland. Localized flooding can occur at the front of the Fraserdelta when a storm or high tide coincides with a Fraser River flood. In both the red and grey zones on themap, small streams, which are not shown at this scale, can also overflow their banks. These relativelysmall floods are triggered by heavy rainstorms.
floodplains
For more detailed information on flood hazard contact the responsible municipal or regional government or the British.Columbia Ministry ofEnvironment, Lands and Parks, Water Management Division.
Earthquake Liquefaction
Lowland (modern sediments)
Mountains (bedrock)
Uplands (Ice age sediments)
Moderate to High(modern lowland sediments)
Low(Ice Age upland sediments)
Nil(bedrock)
0 20kilometres
1
1
Vancouver
RichmondSurrey
Langley
Stra
ito
fG
eo
rgia
FraserRiver
Abbotsford
Mission
White RockSum
asPra
irie
Chilliwack
Physiography of GeoMap
0 20kilometres
A
A’
B
B’
Boundary
Bay
0 20kilometres
high vulnerabilityheavy use
moderate to high vulnerabilitylow to moderate use
Aquifers in Sediment
low vulnerabilitylow to heavy use
< 10
10 - 20
Slope Angle
> 20
high vulnerability
Aquifers in BedrockAquifers not assessed
1
Cascade
Mountains
Earthquake Ground Motion
Canada
USA
USA
Canada
Pacific
Ocean
British
Columbia
0 400kilometres Seismiczones
incre
asin
gseis
mic
hazard
Ground motion, the definitivecharacteristic of earthquakes, causesdamage directly by vibration andindirectly through secondary effectssuch as landslides and liquefaction.Structural design in earthquake-proneareas such as southwestern BritishColumbia is based on anticipated peakhorizontal ground acceleration andvelocity values provided by theGeological Survey of Canada. Theseparameters are derived from statisticalanalysis of past earthquakes andrequire an understanding of the causesof earthquakes in various regions andes t imates of ground mot ionattenuation relationships (how quicklyshaking decreases with distance froman earthquake). This information isincorporated into the National BuildingCode of Canada in the form of seismiczoning maps.
The map to the left shows seismic zones in British Columbia. The zones are based on levels ofpeak horizontal acceleration with a 10% probability of being exceeded over a 50-year period.This acceleration zoning map is centred near 5 Hertz (5 oscillations per second) - a frequencyof ground motion that can damage small or rigid structures. A similar zoning map (notshown) in the National Building Code for peak seismic velocity is centred near 1 Hertz, afrequency that can damage larger structures (e.g. 10-storey buildings). Engineers use thisinformation to design earthquake-resistant structures. These maps represent the intensityof shaking on rock. Local geology and topography may amplify ground shaking at somefrequencies and may de-amplify shaking at other frequencies. There is no map yet forVancouver and the Fraser Valley showing areas of expected ground amplification or de-amplification. The map shown here does not include possible effects of rare, very large,subduction-type earthquakes west of Vancouver Island; shaking produced by theseearthquakes will be considered in the next generation of seismic zoning maps.
Map based on P.W. Basham, D.H. Weichert, F.M. Anglin, and M.J. Berry, 1982, New probabilistic strongseismic ground motion maps of Canada: a compilation of earthquake source zones, methods and results,Geological Survey of Canada, Earth Physics Branch Open File 82-33, 202 pp.
GeoMap VancouverGeological Map of the Vancouver Metropolitan Area
Geological Survey of Canada Open File 3511, 1998
Robert J.W. Turner and John J. Clague;Bertrand J. Groulx, J. Murray Journeay
Bertrand J. Groulx
Robert Cocking, Andrew Makepeace, Kazuharu Shimamura, Sonia Talwar
Design and cartography:
Digital cartography by the GSC Pacific GIS group:
GeoMap Vancouver is available from:Geological Survey of Canada
Sales and Publications
101 - 605 Robson St.
Vancouver, B.C.
V6B 5J3
Tel. (604) 666-0271 Fax. (604) 666-1337
email address: [email protected]
website: www.nrcan.gc.ca/gsc/
Helpful reviews of draft versions of GeoMap Vancouver were provided by John Cassidy, Sandy Colvine, Ron DiLabio, Julian Dunster, Kathy Dunster, John Gartner, Bob Gerath,Susan Heming, Cathie Hickson, Steve Kellas, Nancy Knight, Rosemary Knight, Jack Mollard, Peter Mustard, Jim Roddick, and Alan Whitehead. Bev Vanlier provided editorial assistance.
This map is based on the following Geological Survey of Canadabedrock and surficial geology maps:
Armstrong, J.E. and Hicock, S.R.. Map 1484A (1980).
. Map 1486A (1979).
Amstrong, J.E.. Map 1487A (1980).
. Map 1485A (1980).
Journeay, J.M. and Monger, J.W.H.
.1:50,000-scale map, Open File 2490 (1995).
Roddick, J.A.. Map 1151A (1965).
. Map 1152A, (1965).. Map 1153A, (1965).
Armstrong, J.E. 1990. . Geological Association of Canada, Cordilleran Section, Vancouver, B.C.
Armstrong, J.E. 1984.. Geological Survey of Canada Paper 83-23.
Clague, J.J. 1996. . Geological Survey ofCanada Bulletin 494.
Halstead, E.C. 1986. . Environment Canada, NationalHydrology Research Institute (NHRI) Paper No. 26.
Monger, J.W.H., 1994.Geological Survey of Canada, Bulletin 481.
Turner, R.J.W., Clague, J.J., and Groulx, B.J. 1996.Geological Survey of Canada Open File 3309, poster.
Surficial geology, New Westminister, British ColumbiaSurficial geology, Vancouver, British Columbia
Surficial geology, Chilliwack (west half), British ColumbiaSurficial geology, Mission, British Columbia
Geology and crustal structure of the southern Coastand Intermontane belts, southern Canadian Cordillera, British Columbia
Geology, Pitt Lake (Vancouver, east half), British ColumbiaGeology, Vancouver North, British ColumbiaGeology, Coquitlam, British Columbia
Vancouver geology
Environmental and engineering applications of the surficial geology of the Fraser Lowland,British Columbia
Paleoseismology and seismic hazards, southwestern British Columbia
Ground water supply -- Fraser Lowland, British Columbia
Geology and geological hazards of the Vancouver region, southwestern British Columbia.
Geoscape Vancouver -- living with our geological landscape.
Other publications on geology, geological hazards, and groundwaterof the Vancouver metropolitan area:
ADDITIONAL INFORMATION
1 km
2 km
surface
1 km
2 km
surface
1 km
2 km
surface
A
A’
B
B’
Vertical
exaggeration
of 5 times
in subsurface
Water
Older bedrock(granitic, volcanic, sedimentary)
Sandstone bedrock
Fault(with direction of movement)
Ice Age sediments
Modern sediments
SurfaceSubsurface
projection offault to surface
Beneath Vancouver
see map at leftfor location of
sections A-A', B-B'
This three-dimensional perspective view illustrates thesubsurface geology of Vancouver and the Fraser Valley.Knowledge of geology at depth comes from drill holes andgeophysical surveys. Because this information is limited, theinterpretation shown here is speculative. The diagram showsa deep basin in beneath the Fraser Valley.
filling this basin is more than 4 km thick nearTsawwassen but pinches out at the edges of the basin. Thesandstone, in turn, is overlain by Ice Age sediments up to 1 kmthick. Generally thinner modern sediments are limited to low-lying areas (Fraser delta) and the Strait of Georgia, where theyare currently being deposited. (fractures along whichthere has been movement) offset bedrock and control somelinear features such as Sumas Prairie. These faults are notknown to be active.
granitic rock
Sandstone
Faults
Sumas
Mtn.
Chilliwack
Vedder
Mtn.
Fraser
River
Stave
Lake
Abbotsford
Huntington
Tsawwassen
Sumas
Prairie
Delta
Delta
Boundary Bay
Fraser River
Downtown
Vancouver
Horseshoe
Bay
Howe
Sound
Richmond
B
B’
A
A’
Ge
oM
ap
are
a
0 20kilometres
Squamish
Vancouver
Richmond
Pitt
Lake
India
nA
rm Stave
Lake
Surrey
Langley
Bellingham
Boundary
Bay
FraserRiver
Abbotsford
Mission
White RockSum
asPra
irie
Chilliwack
Hope
Fra
se
rC
an
yo
n
Mt. Baker
Cascade
Mtns
Chuckanut
Hills
Howe
Sound
Harriso
nLake
Stra
itof
Georg
ia
No
oksack
River
CANADA
U.S.A.
Coast MtnsCoast Mtns
Fraser Valley
British
Columbia
GeoMaparea
GeoMap From SpaceThe Fraser Valley is a triangular-shapedlowland bordered by the Coast Mountains,and the Cascade Mountains and ChuckanutHills. The Fraser River, draining a vastinterior basin, breaks through the coastalmountains to reach the Strait of Georgia.
includes that portion ofthe Fraser Valley lying on the Canadian sideof the International Boundary.
GeoMap Vancouver
Geological Map of the Vancouver Metropolitan Area
Geological Survey of Canada Open File 3511, 1998
Ressources naturelles
Canada
Natural Resources
Canada
1842
CANADA
GE
OL
OG
ICA
LS
U
RVEY
- COMMISS
ION
GE
OL
OG
IQU
E
This map provides only a generalized interpretation of liquefaction susceptibilityduring an earthquake and should not be used for local geotechnical evaluation.
Brookswood
aquiferAbbotsford
aquifer
During an earthquake loose water-saturated silts and sands atshallow depth may lose their strength and transform into a fluid( ). Deeper sediments are more consolidated, havehigher confining pressures, and consequently are less likely toliquefy. When sand beneath a layer of silt or clay liquefies, thecapping layer may "glide" laterally under the influence of gravitytowards a slope, such as the bank of a nearby river channel,causing ground cracking. Foundations of highways, bridges,
and buildings, as well as buried sewer and gas lines, can be damaged by such movements. Liquefaction can alsotrigger landslides at the front of the Fraser delta. The red zone shows areas of relatively loose, saturated lowlandsediments (i.e. lowlands). Liquefaction is likely to occur during a strong earthquake in those parts of the red zonewhere there is shallow subsurface sand and coarse silt, for example the Fraser delta.
liquefaction
Physiography
Mountain
uplands
lowlands
is the surface form of the Earth. The Vancouver region includes three main physiographic areas.areas (Coast and Cascade Mountains) comprise rugged bedrock ridges and peaks and intervening steep-
walled valleys. The larger valleys contain thick modern and Ice Age sediments and also host large lakes and streams. Theother two physiographic areas are within the Fraser Valley. Higher parts of the Fraser Valley are gently rolling ,ranging from about 15 m to 250 m above sea level. Uplands are underlain by thick Ice Age sediments, largely of glacialorigin. Flat occur along the Fraser River and its tributaries and are underlain by modern sediments.
Aquifers are bodies of sediment or rock that are saturated and sufficientlypermeable to provide subsurface water to wells. Most groundwater in theFraser Valley is derived from aquifers in modern and Ice Age sediments.These aquifers are a major source of high-quality water for drinking andother uses. The British Columbia Ministry of Environment, Lands and Parkshas classified 71 aquifers in the Fraser Valley according to current levels ofuse and vulnerability to contamination. Almost two-thirds of the aquifersare shallow and can be easily contaminated by downward infiltration ofwaters laced with agricultural fertilizers and pesticides, manure, septiceffluent, or gas and oil from leaking storage tanks. The most heavily utilizedof these highly vulnerable aquifers occur in the Abbotsford andLangley/Brookswood areas. Less developed, but highly vulnerable aquifers
occur in sediments below the floodplain and delta of the Fraser River.Deeper aquifers overlain by silts, clays, or tills of low permeability are lessvulnerable to contamination. The most important of these deep aquifersoccur in the Aldergrove area; others underlie the uplands of Vancouver,Burnaby, Surrey, and Langley, and the lowland of the Nicomekl andSerpentine rivers. Some groundwater is also pumped from fracturedbedrock, for example, at Grant Hill, Mission, and Belcarra. The thin soilcover over these bedrock aquifers makes them highly vulnerable tocontamination. Some aquifers, in both sediments and bedrock, have poorwater quality due to elevated levels of naturally occurring substances suchas chloride, iron, sulphur, and fluoride.
Geo
Map
: Earth (from Greek - Earth); as in geology, the science of the solid Earth
: A visual display of spatial data
geo
GeoMap Vancouver is a geological map of the Vancouver metropolitan area. This area is underlain by diverse geological materials
with different physical properties. The purpose of GeoMap Vancouver is to show the surface distribution of these materials and to
summarize material characteristics that are relevant to engineering, the environment, and land-use planning. Such characteristics
include bearing capacity for structures, landslide potential, liquefaction susceptibility, drainage, flood hazard, and contained
resources such as groundwater, aggregate, and building stone. The legend and central map show the nature and distribution of
the different geological materials. The smaller thematic maps focus on particular attributes and hazards.
Panorama looking southeast over the North Shore, Vancouver city, and the Lower Fraser Valley. The Cascade Mtns and Mt. Baker form the skyline and southern margin of the Fraser Valley. B. J. Groulx
Groundwater and Aquifers
Granitic rockGranitic rocks are a family of medium- to coarse-grained igneous rocks (
).Granitic rocks in the map area range from
165 to 95 million years old. Where not extensively fractured and faulted, granitic rock is resistant to erosion andcan form steep mountain slopes. Granitic rock is locally quarried for use as building stone and crushed rock (PittRiver).
granite, granodiorite, quartz diorite,diorite They consist of interlocking light-coloured grains of and , and dark-coloured and
, which give the rock a distinctive "salt-and-pepper" texture.feldspar quartz biotite
hornblende
1 cm
Stawamus Chief near SquamishT. Turner
Close-up view of granitic rockJ.J. Clague
Volcanic rockDark, fine grained volcanic rocks, chiefly and , are exposed at the northern edge of the FraserValley. These rocks formed as lavas, shallow intrusions, and volcanic ash deposits. Most volcanic rocks areresistant to erosion and form prominent hills in the Fraser Valley (Sentinel Hill, Queen Elizabeth Park, Grant Hill).Young volcanic rocks (35-17 million years old) occur as thick tabular , parallel to the layers in the rocks intowhich they were injected (Grant Hill) and as smaller subvertical that cut across rock layering (ProspectPoint, Stanley Park). Much older ( volcanic rocks are exposed on Sumas Mountain and nearthe confluence of the Harrison and Fraser rivers.
basalt andesite
sills
dykes
185 million years)
Queen Elizabeth Park -- an old basalt quarry turned into a gardenJ.J. Clague
Basalt with columnar jointing, near WhistlerJ.J. Clague
Gravel and sandDeposits of gravel and sand occur along steep-gradient streams in mountain valleys (Chilliwack Valley), onalluvial fans and marine deltas at valley mouths (Capilano and Seymour rivers, North Vancouver), and on islandsand bars of the Fraser River upstream of Mission. G also occur as beach deposits (Jericho, WhiteRock) and as debris cones and fans at the base of mountain slopes. Most areas mapped as are atrisk of flooding and have a moderate to high liquefaction potential. deposits are(they transmit water), and are thus important shallow . They are also potential sources of aggregate, butshallow water tables limit their use for this purpose.
ravel and sandgravel and sand
Gravel and sand permeable
aquifers
LandfillLandfill is material deposited by humans. Fill materials have been dumped in shallow waters and on tidal flatsand other wetlands to extend the area of useable land. Recent recognition of the ecological importance of areasdestroyed by this practice has led to limitations on placements of fills. Landfill in the Vancouver area is foundmainly along shorelines, both marine (False Creek and Burrard Inlet) and river (Annacis Island). It isheterogeneous and includes sand and gravel, till, and/or crushed rock. Landfill also includes waste materialsdisposed of in municipal dumps (Burns Bog in Delta, Port Mann landfill); these dumps can contribute leachatesto local surface and groundwaters and therefore require containment systems. Poorly designed and compactedlandfills can be problematic for foundations, and could liquefy and settle during a strong earthquake.
PeatPeat is partly decomposed plant material found below bogs, swamps, and marshes. Peat up to 5 m thick coversmuch of the Fraser delta east of Highway 99 and the Nicomekl-Serpentine lowland. It also occurs locally on theFraser River floodplain between New Westminster and Mission, at the base of some upland escarpments, atmountain fronts, and within poorly drained depressions in upland areas. Several bogs (e.g. Pitt Meadows bog,Burns Bog) have been mined for sphagnum peat moss, and the peatlands on the Fraser delta are importantproducers of blueberries and cranberries. Because of their high compressibility, peats are extremely poorfoundation materials. Recognition of the ecological importance of bogs has led to increased efforts to protectthem from development.
Silt and claySilt, clay, and loam (mixed clay, silt, and sand) are common on the Fraser River floodplain below Mission, the PittRiver floodplain (Pitt Polder), the Fraser delta, and the Nicomekl-Serpentine flats. These sediments weredeposited over thousands of years by seasonal floodwaters that spread across these lowlands. Silt and claybeneath the Nicomekl-Serpentine flats are ancient marine deposits. They were formed by the slow settling of fineriver-borne sediment onto the sea floor. These fine-grained sediments make poor foundation materials becauseof their low bearing capacity, but are generally not prone to liquefaction. They are important agricultural soils,although poor drainage can be a problem.
Sand and siltInterlayered sand, silt, and loam underlie parts of Sumas Prairie, the Fraser River floodplain downstream ofMission, and the Fraser delta. Similar sediments also occur along some small streams. The unit,like the aforementioned unit, was deposited during floods. Construction of dykes has greatlyreduced such flooding and interrupted the natural deposition of these materials. Sand and silt are importantagricultural soils and can be important shallow groundwater reservoirs ( ). Sand-rich deposits havemoderate to high bearing capacity and are good foundation materials, but could liquefy during a strongearthquake.
sand and siltsilt and clay
aquifers
Modern Sediments in LowlandsAbout half of the Fraser Valley is flat, flood-prone land below 15 m elevation (mainly the of the Fraser River and its tributaries). This area is underlain by loose, water-saturated sediments that are less than 10,000 years old(i.e. age). Fraser River floodplain sediments consist mainly of gravel and sand from Hope to Mission; sand and silt dominate farther downstream. The Nicomekl-Serpentine and Pitt River valleys and Sumas Prairie areunderlain by sand and silt. Poorly drained areas of floodplain are mantled by peat, and landfill has locally extended shorelines. Floodplains contain rich agricultural soils, but are generally poorly drained due to the flat terrain andshallow water table. Although still predominantly rural, some lowlands are areas of rapid urban growth (Richmond). Most communities on floodplains are protected by dykes from all but the largest floods.
floodplainsHolocene
1 m
1 m
Sand landfill along False CreekJ.J. Clague
Port Mann landfillR. Turner
Mined peat area, Burns Bog, Fraser deltaJ.J. Clague
Peat layers exposed in excavationJ.J. Clague
Tidal mud, Serpentine River estuaryA.C. Clague
Modern clayey silt, Serpentine River estuaryA.C. Clague
Locarno BeachJ.J. Clague
Beach sandJ.J. Clague
River bar, Capilano RiverR. Turner
River gravelR. Turner
Ice Age Sediments in UplandsIce Age sediments deposited during the (2 million to 11,000 years ago) underlie gently rolling uplands (15 to 250 m elevation) of the Fraser Valley. Most Ice Age sediments in the Vancouver area date to the lastglaciation, about 25,000 to 11,000 years ago, and in particular to the period of glacier retreat when areas below 200 m elevation were covered by the sea. These sediments include deposited directly by glaciers, gravel and sand laiddown by streams flowing off the melting ice ( ), marine clay and silt, and beach gravel and sand. Deposits older than the last glaciation are only exposed in steep escarpments along the margins of uplands. Most cities andtowns in this region were built on the uplands to avoid the flood and drainage problems of lowland areas. Upland sediments are good foundation materials and are generally not susceptible to liquefaction. Soils developed on graveland sand are well drained, whereas those developed on silt, clay, and some till deposits are poorly drained. Flooding is limited to the narrow valley bottoms of small streams incising the uplands.
Pleistocene Epoch
tilloutwash
Silt and clayThick silt and clay of marine origin are the most widespread surface sediments in the Surrey, White Rock, andLangley-Aldergrove uplands. This unit includes massive and bedded sediments with variable bearing capacities,depending partly on whether or not they were overridden and loaded by glaciers. In general, deposits east ofAldergrove have been loaded by ice and thus have higher bearing strengths. Water infiltration is poor becausethe sediments are fine grained; this can result in poor surface drainage if the land is flat. Silt and clay deposits onsteep slopes (>20 ) are prone to landsliding. Silt and clay deposits exposed during construction activities erodeeasily and can be a major source of stream siltation.
o
SandScattered sand deposits up to 5 m thick occur on the Vancouver, Tsawwassen, White Rock, and Surrey uplands;they are absent from uplands east of Langley. The sands are beach deposits that formed when uplands emergedfrom the sea at the end of the last glaciation. They have good bearing strength, but are generally too thin to affectfoundations. Water passes through sands with ease, thus soils developed on these materials are well drained.
Gravel and sandDeposits of gravel and sand up to 40 m thick are widespread on uplands between Langley and Abbotsford, andnorth of the Fraser River between Pitt Meadows and Mission. Important deposits also occur on the North Shore,adjacent to the Capilano, Seymour, and Coquitlam rivers, and in the Columbia Valley south of Cultus Lake.Gravel and sand have high bearing capacity and excellent drainage. Thick gravel and sand deposits are importantsources of aggregate; there are numerous gravel pits south and east of Aldergrove, and south of Langley. Graveland sand are also important (the Abbotsford and Brookswood aquifers). Shallow aquifers arevulnerable to contamination from agricultural and industrial activities.
aquifers
TillTill is a heterogeneous glacial deposit consisting of clay, silt, sand, and stones ranging from pebble to bouldersize. Till up to 25 m thick is the dominant surface and near-surface material over much of the Vancouver upland,where it is overlain by patchy marine silt and sand. Farther east, till is an important, but less extensive surfacematerial; it is buried by thick silt and clay in the Surrey and Aldergrove areas. The lower slopes of the CoastMountains are mantled by up to several metres of till. Some tills are compact and concrete-like, whereas othersare sandy and loose. Till commonly has a high bearing capacity and thus is an excellent foundation material.Compact till is nearly impervious; for good drainage, the surface must slope. Silt- and clay-bearing tills disturbedduring construction activities can be a major source of stream siltation.
Steepland sedimentsSteep escarpments occur locally at the borders of uplands. Escarpments expose Ice Age sediments that,elsewhere on the uplands, are covered by younger sediments, discussed above. These older sediments includeclay, silt, sand, gravel, and . The bases of some escarpments are being actively undercut by ocean waves(Tsawwassen, White Rock, Point Grey) or streams (Chilliwack, Capilano, Seymour, and Coquitlam rivers),making them vulnerable to landsliding. Many residential areas extend to the edges and bases of escarpments;even small slides in these localities can damage or destroy houses, roads, and other structures.
till
20 cm
0.5 m
20 cm
Blocky weathering, massive marine clayJ.J. Clague
Layered silt and clayJ.J. Clague
Layered sand deposited in an ancient lakeJ.J. Clague
Close-up of layered sandJ.J. Clague
Gravel pit, AldergroveJ.J. Clague
Glacial gravelP.T. Bobrowsky
Ridges of till at snout of Coast Mountain glacierJ.J. Clague
Compact tillJ.J. Clague
Buildings near unstable cliff of Ice Age sand and silt, U.B.C.University of B.C.
Residences along a steep coastal bluff, TsawwassenJ.J. Clague
Bedrock in MountainsSolid bedrock forms the Coast and Cascade Mountains, as well as smaller mountains that protrude through thick sediments in the Fraser Valley (Burnaby Mountain, Grant Hill, Sumas Mountain, Chilliwack Mountain). Bedrock iscommonly mantled by several metres of till, sandy gravel, or rock fragments; less than 10% of the mountain area is actually exposed rock. Bedrock in this region can be grouped into four main units described below. Landslides occurwhere weak rocks are exposed on steep slopes. Rock weakness can stem from the presence of faults, fractures, sedimentary layers, or platy mineral layers ( ) that dip in the direction of the slope. Thin sediments overlyingbedrock can slide into stream channels during rainstorms, triggering flows of sediment, water, and plant debris ( ) that move downstream at high velocity.
foliation
debris flows
SandstoneSandstone, siltstone, and conglomerate (85-37 million years old) occur as scattered outcrops in Vancouver,Burnaby, and on the North Shore (Stanley Park, Kitsilano, Burnaby Mountain, Capilano River). These rocks alsooccur at depth through much of the Fraser Valley. Sandstone layers resistant to erosion and tilted down to thesouth form ridges with steep north-facing bluffs and gentler south-facing slopes (Burnaby Mountain, StanleyPark). Ridges are separated by valleys eroded into softer siltstone (First Narrows, Burrard Inlet). These rocksare weakly cemented and can be excavated without blasting. About 5-15% of the rock is open pore space makingdeeply buried sandstones potential natural gas reservoirs.
2 cm
Polished slab of sandstoneJ.J. Clague
Layered sandstone and siltstone, Sumas MountainP.S. Mustard
Foliated sedimentary and volcanic rockMetamorphosed sedimentary and volcanic rocks occur widely in the Cascade Mountains, and also form smallhills in the eastern Fraser Valley (Chilliwack Mountain). These rocks are characterized by a planar fabric( ) formed during burial, deformation, and metamorphism of the rock. This fabric reduces rock strength,causing some rock types to weather into thin platy fragments. Bedrock exposed on Vedder Mountain and east ofCultus Lake is made up of thinly layered, dark , and lesser , , , and .Volcanic rock with interlayers of limestone, argillite, and sandstone is exposed on mountain slopes in the upperChilliwack River basin.
foliation
argillite phyllite gneiss limestone chert
20 cm
Folds in interlayered sandstone and argilliteJ.M. Journeay
Platy weathering of strongly foliated phylliteJ.J. Clague
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