Chapter 16Chapter 16

Geology and Nonrenewable Geology and Nonrenewable Mineral ResourcesMineral Resources

What is the Earth’s Structure?What is the Earth’s Structure?

• Core: Earth’s innermost zone; very hot; solid inner part surrounded by a liquid core

• Mantle: surrounds the core; mostly solid rock; outermost part is very hot, partly melted rock (like flowing plastic)

• Crust: outermost and thinnest zone; consists of the continental crust (underlies continents) and the oceanic crust (underlines oceans)

Mantle

Core

Crust

Low-velocity zone

Solid

Outer core(liquid)

Innercore(solid)

35 km (21 mi.) avg., 1,200˚C

2,900km(1,800 mi.)3,700˚C

5,200 km (3,100 mi.), 4,300˚C

10 to 65km

100 km

200 km

100 km (60 mi.)200 km (120 mi.)

Oceanic crust(lithosphere)

Abyssalfloor

Oceanicridge

Trench

Volcanoes

Mantle (lithosphere)

Mantle (asthenosphere)

Ab

ys

sa

l p

lain

Continental crust(lithosphere)

Mantle(lithosphere)

Continentalslope

Continentalshelf Abyssal plain

Abyssalfloor

Earth’s Crust and MantleEarth’s Crust and Mantle

Movement of Heat within the EarthMovement of Heat within the Earth

• Internal Processes: originate from the Earth’s interior

• Decay of radioactive elements in the crust adds to heat within the mantle

• Two types of heat movement happen inside the mantle:

1. Convection Cells: large volumes of heated rock move (like pot of boiling water)

2. Mantle Plumes: mantle rock flows upward in a column (like smoke from a chimney)

What are Tectonic Plates?What are Tectonic Plates?

• Convection cells and mantle plumes both move upward as heated material is displaced by cooler, sinking material

• These flows of energy cause movement of “tectonic plates”

• Plates are about 60 miles thick

• Composed of continental and oceanic crust, and the outermost part of the mantle

Tectonic plate

Collision between two continents

Oceanic tectonicplate

Spreading center Oceanic tectonic

plateOcean trench

Plate movement Plate movement

Continentalcrust

Oceaniccrust

Continentalcrust

Mantle

Innercore

Hot outercore

Two plates movetowards each other.

Hot materialrisingthroughthe mantle

Material coolsas it reachesthe outer mantle

Cold densematerial fallsback throughmantle

More about Plate TectonicsMore about Plate Tectonics

• Tectonic plates move constantly, like large pieces of ice on lake surface

• Move about the rate of fingernails growing

• Widely accepted theory in the 60s.

• Throughout history, continents have drifted apart and joined together as plates move back and forth across Earth’s surface

More about Plate TectonicsMore about Plate Tectonics

• Produces mountain and ocean ridges

• Volcanoes and earthquakes are found at plate boundaries

• Allows us to trace how species migrated from one area to another

Volcanoes Earthquakes

Earthquake and Volcano SitesEarthquake and Volcano Sites

Boundaries Between Earth’s PlatesBoundaries Between Earth’s Plates

• Divergent Plate Boundaries: plates move in opposite directions

• Convergent Plate Boundaries: plates are pushed together by internal forces; forms a trench

• Transform Faults: occur where plates slide past one another; most are on the ocean floor

Between Earth’s PlatesBetween Earth’s Plates

• External Processes: geological changes based on energy from the sun or gravity

• Erosion: material is dissolved, loosened, or worn away from one part of the Earth’s surface and THEN deposited in other places

• Wind can cause erosion as soil is blown from one area to another

• Human activities accelerate erosion

Continued…Continued…

• Weathering: process that loosens material that can be eroded

• Two Types of Weathering:1. Mechanical Weathering: large rock mass

is broken into smaller fragments; Frost Wedging (water collects in pores of rocks, expands, and splits rock)

2. Chemical Weathering: chemical reactions decompose a mass of rock

Dunes Lagoon

SpitsStream

Glacier

Lake

Tidalflat

Barrierislands

Shallow marineenvironment

Volcanicisland

Coral reef

Abyssal plain

Continental shelf

Continental slope

Continental rise

DeltaDunes

Beach

Shallow marineenvironment

Minerals and RocksMinerals and Rocks

• Earth’s crust is composed of minerals and rocks

• Mineral: element or inorganic compound that occurs naturally and is solid (gold, silver, salt, quartz)

• Rock: any material that makes up a large, natural, continuous part of the Earth’s crust; most rocks consists of two or more minerals

Three Major Types of RocksThree Major Types of Rocks

1. Igneous Rock: formed below or on Earth’s surface when magma (molten rock) wells up, cools, and hardens into rock (granite, lava rock)

2. Sedimentary Rock: formed from sediment when rocks are eroded, transported to another place, and deposited in water (sandstone)

3. Metamorphic Rock: rock is subjected to high temperature, high pressure, or chemically active fluids (coal, slate, marble)

Rock CycleRock Cycle

• Rocks are constantly exposed to changing conditions

• Interaction of processes that change rocks from one type to another is called the Rock Cycle

• Slowest of all Earth’s cycles; recycles material over millions of years

Igneous RockGranite, pumice,

basalt

Metamorphic RockSlate, marble,

Magma(molten rock)

Cooling

Heat, pressure

Melting

Heat,pressure,

stress

Sedimentary Rocksandstone,limestoneDepositionTransportation

Erosion

Weathering EXTERNAL PROCESSES

INTERNAL PROCESSES

ROCK CYCLE

EarthquakesEarthquakes

• Stress in the Earth’s crust can cause solid rock to deform until it fractures and shifts along the fracture (fault)

• Abrupt movement of an existing fault causes an earthquake

• When fracture happens, energy is released as shock waves

Measuring EarthquakesMeasuring Earthquakes

• Magnitude: severity of an earthquake

• Measure amount of energy released in an earthquake

• Categories: insignificant, minor, damaging, destructive, major, great

• Each level is 10x greater than the previous

How Can We Reduce How Can We Reduce Earthquake Hazards?Earthquake Hazards?

• Examine historical records and make measurements to locate active fault zones

• Make maps to show high-risk areas

• Establish building codes for high-risk areas

• Try to predict where and when earthquakes will occur

VolcanoesVolcanoes

• Occurs where magma (molten rock) reaches the Earth’s surface through a crack

• Volcanic activity can release: debris (hot lava rock or ash), liquid lava, gases

• These gases may become concentrated in the atmosphere and become concentrated into sulfuric acid

extinctvolcanoes

magmareservoir

centralvent

lithosphere

Upwellingmagma

Volcano

Aftermath of VolcanoesAftermath of Volcanoes

• Between 1985 and 1999: 561,000 people died from natural disasters; about 30% of these were from earthquakes and volcanic eruptions

• Benefits: scenery, lakes (Crater Lake in Oregon), fertile soil from weathering lava

How Can We Reduce Volcano How Can We Reduce Volcano Hazards?Hazards?

• Land-use planning

• Better prediction of volcanic eruptions

• Evacuation plans