The Solid Earth

Earth’s Structure

• Core

• Mantle

• Crust

Earth’s Structure

Earth’s Structure

Core

• Innermost portion of the earth

• Inner core is VERY hot, but solid

• Outer core is liquid molten material

Mantle

• Surrounds the core

• Most is solid rock, but under the outermost part is a zone of hot, partly melted rock that flows like soft plastic called the asthenosphere

Crust

• Outermost and thinnest layer

• Continental crust-under continents

• Oceanic crust-under the oceans (71% of the crust)

Internal Earth Processes

• 2 kinds of movement of the earth– Convection cells: large volumes of heated

rock that move following a pattern similar to the atmosphere (warmer is less dense)

– Mantle plumes: mantle rock flows slowly upward, reaching the surface and spreading out (oceanic ridge)

Convection Currents

Mantle Plume

Plate Tectonics

• Tectonic plates (~60miles thick) consist of continental and oceanic crust and rigid outermost part of the mantle-called the lithosphere

• Plates move constantly supported by the flowing asthenosphere

• Produces mountains, oceanic ridges, trenches, etc.

Plate Movment

Plate Tectonics

3 Types of Plate Boundaries

• Divergent plate boundary: plates move apart from each other

• Convergent plate boundary: plates moving toward each other (earthquakes)

• Transform Fault: plates slide past each other

Divergent Plate Boundary

Convergent Plate Boundary

Transform Fault

• http://www.youtube.com/watch?v=QDqskltCixA

External Earth Processes

• Geologic changes based directly or indirectly on energy from the sun and gravity– Erosion– Weathering

Erosion

Erosion

• Material is dissolved, loosened, or worn away from one part of the earth’s surface and deposited in other places– Streams– Wind– Human activities that accelerate erosion (acid

rain)

Weathering

• Produces loosened materials that can be eroded

• Two types– Mechanical (frost)– chemical

Minerals

• An element or inorganic compound that occurs naturally (solid)– Can be an element (gold)– Can be a combination of elements (salt,

quartz)

Rocks

• Material that makes up a large, natural continuous part of the crust– Most consist of 2 or more minerals

Three main Rock Types

• Igneous

• Sedimentary

• Metamorphic

Igneous

• Formed when magma (molten lava) wells up, cools, and hardens; most of the earth’s crust– Granite– Lava

Igneous

Sedimentary

• Formed from sediment that is weathered into smaller pieces, transported, and deposited into a body of water, pressed together, forming layers– Sandstone– limestone

Sedimentary

Metamorphic

• Formed when preexisting rock partially melts, or is subjected to high pressure– Slate– marble

Metamorphic

Rock Cycle

Natural Hazards-Earthquakes

• Stress in the earth’s crust cause a fracture in solid rock, producing a fault

• Energy is released as shock waves moving outward from the focus– Focus: point of initial movement– Epicenter: point on the surface directly above

the focus

Earthquakes

Earthquakes

• Magnitude measured by the Richter Scale• Seismograph measures amplitude of vibrations

(each unit represents an amplitude that is 10X greater than the one before it) ex. An earthquake of 6.0 is 100x greater than a 4.0– Insignificant <4.0– Minor 4.0-4.9– Damaging 5.0-5.9– Destructive 6.0-6.9– Major 7.0-7.9– Great >8.0

Seismogram

Earthquakes

• Aftershocks can last up to 4 months• Foreshocks can occur seconds to weeks before

main shock• Primary Effects: shaking, permanent ground

displacement, damage to infrastructure• Secondary Effects: rock slides, urban fires,

flooding, tsunamis• http://www.youtube.com/watch?

v=g15sZ_d2WUY

Natural Hazards-Volcanoes

• Magma reaching the earth’s surface• Can release:

– Ejecta (rocks, debris)– Liquid lava– Gases (water vapor, carbon dioxide, sulfur dioxide)

• Concentrated where there is seismic activity• Gases can remain in the atmosphere for up to 3 years,

causing a cooling effect by as much as 1oF• http://www.youtube.com/watch?v=bgRnVhbfIKQ

• http://www.youtube.com/watch?v=Hec9yK-QQ4o

Volcanoes

Earthquake/Volcanic Activity