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Planet Earth

Use with Holt Physical Science, Chapter 21

Eowyn Johnson

on 22 February 2013

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Transcript of Planet Earth

PLANET EARTH Earth's Interior and Plate Tectonics What is Earth's Interior Like? Plate Tectonics Plate Boundaries Less dense than oceanic crust
Thicker than oceanic crust Denser than continental crust
Composed of basalt Outer layer of Earth's structure
Includes crust and upper mantle Plastic layer in the upper mantle (80-200 km deep) Named after Yugoslavian seismologist
Separates crust from mantle Important People:
Alfred Wegner
Sir Edward Bullard Evidence
Fit of the continents
The fossil record
Magnetic dip The Wilson Cycle Earthquakes (Red Sea) (Atlantic Ocean) (Pacific Ocean) (Cascade Mountains) How the Tectonic Plates are Involved The movement of plates stresses rocks near plate edges Three types of force act on rocks: Tension--cause normal faults
Compression--cause reverse faults
Shear--strike-slip fault Volcanoes Rocks and Minerals Rock Cycle Song
(Sing to the tune of "Row, Row, Row Your Boat")

Has been found formed in layers
Often found near water sources
With fossils from decayers

Then there's IGNEOUS rock
Here since Earth was born
Molten lava, cooled and hardened
That's how it is formed

These two types of rocks
Can also be transformed
With pressure, heat and chemicals
METAMORPHIC they'll become Where Can We Find Volcanoes?

1. Usually at convergent plate boundaries

2. Underwater at divergent plate boundaires

3. Middle of plates in hot spots Anatomy of a Volcano Types of Volcanoes Cinder Cones Composite Shield Lava Dome Simplest type of volcano
Singl vent
Bowl-shaped crater
Violent eruptions caused by gas-charged lava which breaks into small fragements (cinders)
February 20, 1943 Paricutin grew to a few hundred meters high in a Mexican corn field over a few days. Typically steep-sided
Alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs
Examples: Mount Fuji, Mount St. Helens
Usually contain a central vent or a clustered group of vents
Contain conduit system thorough which magma from a reservoir deep in Earth's crust rises to the surface
High amount of gases trapped in magma cause varied eruptions Built almost entirely of fluid lava flows
Flow after flow pours out in all directions creating a gently sloping cone
Built slowly by accretion of thousands of highly fluid lava flows
Examples: Kilauea and Mauna Loa in Hawaii
Mild eruptions Formed by relatively small masses of lava too viscous to flow any great distance
Lava piles over and around the vent
Dome grows largely by expansion from within
Usually occur within craters or on the flanks of large composite volcanoes Dating Rocks Relative Dating Radioactive Dating Weathering
Erosion Chemical weathering occurs when the chemical composition of a substance changes. Water Ice Wind Physical Weathering (mechanical weathering) breaks rock into smaller pieces. The chemcial compositon is not changed. Sea Level Change Isostatic changes occur due to accumulation or removal of heavy loads of ice, sediment, or lavea
During the last 3.5 - 3 million years four major accumulations of ice developed in high latitudes The ice that once covered Asia, Europe and North America has mostly melted
When they were under the ice sheet, they were pushed down and are still recovering
Some geologists believe isostatic rebound will eventually cause the Hudson Bay floor (150 m deep) to rise above sea level. WEATHERING Our Goals Distinguish between chemical and physical weathering
Describe the importance of water to weathering
Identify examples of chemical and physical weathering Physical and Chemical Weathering The Old Man of the Mountain First carved by glaciers.
Freezing and thawing caused fissures in the "forehead."
Mineral in granite, perthite, was altered to kaolinite.
Collapsed in 2003.
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