The Earth’s Structure

Inside the Earth• Age of the Earth- Believed to be 4.6 Billion Years Old!• Core: The center of the earth that consists of very hot

metal, iron and nickel. Two Parts:

1. Inner Core: Dense and solid.2. Outer Core: Molten (liquid) metal.

• Mantle– Thick layer of rock.– 1,800 miles thick– Mostly solid, but contains pockets of magma (melted rock)

• Crust– Very thin Think of frosting on a cake.– Thinnest parts are beneath the ocean (5 miles)– Thickest parts lie beneath the continents (22 miles)

Inside the Earth- Diagrams

Land and Water

• The earth is 70% water.

• Continents: Large landmasses in the Ocean

– 7 continents (Asia, Australia, North America, South America, Europe, Antarctica, and Africa)

– Asia (largest) and Australia (smallest)

Land and Water• Landforms are classified

according to differences in relief.

– Relief: The difference in elevation between the highest and lowest points.

– Major types of landforms:1. Mountains At least

2,000 ft.2. Hills: lower, rounded,

and less steep than a mountain.

3. Plateaus: a raised area, with a level surface

4. Plains: A flat, or gently rolling area where there are few changes in elevation.

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How are landforms Created and Shaped?

• Landforms are created and shaped by internal forces:• 1. Volcanism: Movement of magma inside the earth.

• Volcanoes form when magma (molten rock inside the earth) breaks through the earth’s crust.

• What is Lava? • On the surface, magma becomes lava and may flow to create a plateau-like shield volcano.• What might the Ash and cinders create from the eruption? • small cinder cones.• What is a Cone-Shaped Mountain? • Alternating sequences of explosive eruptions and smooth lava flows. Ex: Mount Fuji in Japan.

How are Landforms Created and Shaped Cont.

2. Changes in the earth’s crust by movements that fold, lift, bend, or break rock of the crust.

– Fold: » When rock layers bend and buckle.

– Faults: » Breaks in the Earth’s crust.o Both sides of the fault rub against each other: sideways, up or down.

o Slow movement subtle, almost unnoticeable changes.o Large, sudden movement (slip or displacement)

EARTHQUAKE! Epicenter Center of the earthquake.

• http://video.nationalgeographic.com/video/player/environment/environment-natural-disasters/earthquakes/earthquake-montage.html

Why does California have so many Earthquakes?

• Plate Tectonics• Theory says:

– the earth’s crust is broken into a number of moving plates.– Plates vary in size and thickness.– Plates slide over a hot layer of the mantle. – Oceans and continents are on top of the plates.

• California – San Andreas Fault– Most earthquakes and volcanoes are located along where

plates meet.

- Example of Earthquakes- http://video.nationalgeographic.com/video/player/environment/environment-natural-disasters/earthquakes/earthquake-montage.html

- Response: What would you do?- Share with your neighbor

•Underwater Volcanoes - http://video.nationalgeographic.com/video/player/news/environment-news/west-mata-submarine-volcano-vin.html

•Are there any animals around? Why?

Why does California Have So

Many Earthquakes Cont. • Continental Drift

Theory – Jigsaw puzzle

• There was once a single supercontinent called Pangea about 180 million years ago.

• Over time Pangea began to break apart.

• Proof:– Fossils of animals and

plants from South America, Africa, India, and Australia were almost identical

Why does California have so

Many Earthquakes Cont. • Seafloor Spreading Theory

• Magma from the mantle rises under the underwater ridge and breaks through a split at the top of the ridge.

• Result is called a Rift Valley• The rock then spreads out in both directions from the ridge • As the seafloor moves away from the ridge, it carries away older

rocks.• The ocean floor is not flat Landforms look the same in the

water and on land.• Ridge System : • underwater mountains that extend around the world (40,000

miles).• Rocks in the ocean are newer than the ones on land.• Both seafloor spreading and continental drift are part of the

theory of Plate Tectonics.

Plate Movement

• Plate Movement: • How do the continents move? • Convection: A circular movement caused

when a material is heated, expands, and rises, then cools and falls.

– Occurring in the mantle.• Example: Hot air rising

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es0805/es0805page01.cfm

Four Major Types of Plate Movement

• 1. Spreading: When plates pull away from one another and form a spreading zone with molten rock pushing through to the surface.

– These areas are likely to have a rift valley, earthquakes, and volcanoes.

• 2. Subduction: When an oceanic plate meets a continental plate, it slides under the continental plate and down into the mantle and melts in the mantle eventually coming back to the earth in the form of volcanic activity.

– Oceanic Plate is heavier so it goes under the continental plate.

– Example: Andes Mountains– http://www.classzone.com/books/earth_science/terc/conten

t/visualizations/es0902/es0902page01.cfm

Four Major Types of Movement Cont.

• 3. Converging: When two plates of the same type meet.

– Two oceanic plates, one slides under the other Usually forms an island group.

– Two continental plates, the plates push against each other creating mountain ranges.

» Example: Himalayas

• 4. Faulting: When plates slip or grind past each other along faults.

– Example: San Andreas Fault

Convergent

Faulting

Volcanoes and Plate Tectonics

• Most volcano eruptions occur along plate boundaries.

– Example: Ring of Fire • Chains of Islands are formed by hot spots • Hot Spots: Regions deep within the mantle that

produce magma that rises toward the earth’s surface.

• When the molten rock rises from a hot spot, it produces hot springs or geysers, or island chains.

• Example: Hawaii (stationary hot spot while plate continues to move)

Ring of Fire!