VOLCANIC ACTIVITY
description
Transcript of VOLCANIC ACTIVITY
![Page 1: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/1.jpg)
VOLCANIC ACTIVITY18.1 Magma
![Page 2: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/2.jpg)
Magma Molten rock, mineral
grains, and dissolved gasses deep inside Earth
Rocks begin to melt at 800o-1200oC
Depth, pressure and melting point have a direct relationship
However, wet rock melts at a lower temperature (p.472)
![Page 3: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/3.jpg)
Types of Magma Basaltic- Hawaiian Islands Andesitic- Mount St. Helens Rhyolitic- Yellowstone National Park
![Page 4: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/4.jpg)
Magma Composition Viscosity- resistance to flow Basaltic- low viscosity, low
gas, low silica, quiet eruptions Andesitic- found near
subduction zones, intermediate viscosity, 60% silica, intermediate eruptions
Rhyolitic- high silica, high gas, very explosive!
![Page 5: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/5.jpg)
Viscosity Hotter = less viscous Basaltic lava
temperatures = 1000o- 1250oC
Rhyolitic lava temperatures = 700o- 900oC
More silica = higher viscosity
![Page 6: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/6.jpg)
![Page 7: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/7.jpg)
VOLCANIC ACTIVITY18.2 Intrusive Activity
![Page 8: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/8.jpg)
Plutons Bodies of
intrusive igneous rock
Exposed on the surface by erosion
![Page 9: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/9.jpg)
Batholiths- large formations that spread over at least 100 km2
Stocks- similar to batholiths but cover less than 100 km2 at the surface.
![Page 10: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/10.jpg)
Laccolith- mushroom-shaped; form when magma flows between rock layers and pushes up the overlying rock layers.
![Page 11: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/11.jpg)
Sill- parallel to surrounding rock layers.
Dike- cuts across layers of rock.
Sills and dikes vary in thickness from a few centimeters to hundreds of meters.
![Page 12: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/12.jpg)
Plutons and Tectonics Plutons are caused by mountain-
building processes along convergent plate boundaries.
![Page 13: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/13.jpg)
VOLCANIC ACTIVITY18.3 Volcanoes
![Page 14: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/14.jpg)
Anatomy of a Volcano Lava erupts through openings in the
crust called vents. Bowl shaped areas atop vents are called craters.
![Page 15: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/15.jpg)
Volcanoes can collapse and form larger depressions called calderas.
![Page 16: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/16.jpg)
Types of Volcanoes Shield- broad, gentle
slope; non-explosive means of formation
Cinder-cone- small, steep sides, explosive; formed by piled debris
Composite- violent; composed of fragments and solidified lava
![Page 17: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/17.jpg)
Volcanic Material Tephra- rock fragments thrown into the
air by an eruption Classified by size: dust, ash, lapilli,
volcanic blocks and volcanic bombs Blocks are angular; bombs are rounded
![Page 18: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/18.jpg)
Pyroclastic Flow Rapidly moving
cloud of volcanic materialSpeeds can
exceed 100 mph - 450 mph
Temperatures can reach 1800oF
![Page 19: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/19.jpg)
![Page 20: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/20.jpg)
Where Do Volcanoes Occur? Convergent boundaries- subduction zones
where magma is forced upward Divergent boundaries- magma is forced
upward at ridges, rifts, fractures and faults
![Page 21: VOLCANIC ACTIVITY](https://reader036.fdocuments.us/reader036/viewer/2022062315/5681658e550346895dd85b22/html5/thumbnails/21.jpg)
Where Do Volcanoes Occur? Hotspots- hot stationary plumes of magma far
from plate boundaries