Earth’s Structure

Unit CChapter 7 Lesson 1

C38 – C45

OBJECTIVES

• Identify and describe Earth’s layers.

• Recognize that Earth’s lithosphere is broken into plates that move slowly across Earth’s surface.

• Recognize that the rock record shows Earth’s continents have moved across time.

MAIN IDEA

• Earth has a layered structure. Its outer layer is made up of moving plates.

CORE

• Earth’s innermost structure.• Divided into two regions.• Outer core 1,400mi thick

and is the only layer in liquid state

• Inner core 720mi thick is the hottest layer mad up of iron & nickel, but the pressure keeps the metal from melting

CRUST• Thin, nearly solid

rock layer that is uppermost in Earth’s structure.

• Thinnest layer• Nearly solid rock.• Thickness under the

continents is 24miles• Under mountains

42miles• Under ocean-floor

about 4mi.

LITHOSPHERE

• Area where Earth’s solid upper mantle and crust combine to form a rigid shell.

• Floats on the mantle

MANTLE• Thick layer of

Earth’s structure just below Earth’s crust.

• 2,900km (1,800mi) thick

• Makes up 2/3 of Earth’s mass

• Rock material is partially melted

PLATE TECTONICS• Idea that giant plates

or rock are moving slowly across Earth’s surface

Hot Inside

• Geysers – hot water shooting up for Earth’s surface.

• Water drains deep into Earth’s surface.• How rocks heat up water until steam

forms• Pressure forces the remaining water to

erupt• Yellowstone National Park in Wyoming

has may geysers.

Earth’s Temperature

• Temperature increases 2 – 3 degrees C for every 0.1km (300ft) below the surface.

• The deepest holes ever drilled are less than 15km (9mi).

• Geysers, Volcanoes, seismic waves help scientist learn about earth’s interior.

MOVING PLATES - 1915

• Alfred Wegener, German meteorologist & geologist

• Felt continents were moving slowly across Earth’s surface

• Wegener’s theory is known as The Theory of Continental Drift

• His theory was rejected

MOVING PLATES - 1950

• Scientist believed the lithosphere was broken up into giant slabs of rock called plates.

• This idea is called Plate Tectonics.• They move an average speed of 4

inches per year• Two kinds of plates: Oceanic plates &

Continental plates

PLATES

• Oceanic Plates

• Consist of dense ocean-floor material

• Continental plates

• Made up of lighter continental rock “riding” on top of denser rock

Converging Boundaries

• Two plates move toward each other.

• One plate may move under the other in a process called subduction.

• Oceanic & Continental plates converge.

• Denser rock of oceanic plate slides under the lighter continental plate

Diverging Boundaries

• Two plates move away from each other.

• Molten rock rises to fill the gap, creating new crust.

• Usually happens in the middle of the ocean floor

• Referred to as sea-floor spreading

Sliding Boundaries

• Two plates slide past each other, moving in opposite directions.

• This happens along what is known as a fault line.

Evidence for Moving Plates

• Rocks• Studying the layers of rocks shows

how they were deposited• Fossils – the physical remains or

traces of plant or animal that lived long ago

• Fossils found in sedimentary rock

Fossils

• Fossils of similar species have been discovered on opposite sides of an ocean.

• This helps scientist understand how plates move.

• Fossils of tropical plants and animals have been found in polar regions.

PHOTO - CAMBRIAN TRILOBITE

Earth’s _____, consists of metals.

• Inner core

Where the upper mantle and crust meet.

• Lithosphere

______ is a theory that describes how large slabs of the lithosphere move..

• Plate Tectonics

Which is the thickest of Earth’s layers?

• Mantle

How can fossils provide evidence to support the

theory of plate tectonics?

• Fossils of tropical plants and animals may be found in polar regions.

List three ways scientist can learn more about what goes on beneath

Earth’s surface.

• Study rocks drilled from the crust• Volcanoes• Geysers

Measurements indicate that the distance between Africa and South America is increasing. What do these measurements indicate about the portion of

Earth’s crust between Africa & South America?

• Africa & South America are located on different plates. There is a diverging boundary between the two plates.

Explain what happens to rock along converging boundaries.

• Plates collide and rocks compress and break. One plate may move below the other plate.

Besides plate movement, describe one process that can alter the structure of Earth’s

mantle.

• Weathering, erosion, or depostion can create plateaus, mesas, caves, sand dunes, alluvial fans, barrier islands

Describe evidence of high temperatures below Earth’s

surface.

• Scientists encounter higher temperatures when they drill.

• Rocks melt below the Earth’s surface.• Geysers spew hot water from beneath

the surface.

Describe one way mountains may have formed.

• Magma rose near the surface but did not break through.

• Faulting caused one plate to rise above another plate.

• Erosion by wind and rain rounded the surface over time.