1 - Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is.

1 - Earth’s LayersThe Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed.

This crust is not a solid shell; it is broken up into huge, thick pieces (Plates) that drift on top of the soft, underlying mantle.

2 - The Crust

• Outermost layer• 5 – 100 km thick• Made of Oxygen, Silicon, Aluminum

3 - The Mantle

• Layer of Earth between the crust and the core

• Contains most of the Earth’s mass

• Has more magnesium and less aluminum and silicon than the crust

• Is denser than the crust

4 - The Core

• Below the mantle and to the center of the Earth

• Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

Convection is like a boiling pot. Heated soup rises to the surface, spreads and begins to cool, and then sinks back to the bottom of the pot where it is reheated and rises again.

5 - Plate TectonicsThe Earth’s crust is broken into pieces also called Plates. The plates (pieces) are moving. The plates’ movement is driven by cooling of Earth (convection).

Modified from USGS Graphics

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6 - Plate Tectonics

• Greek – “tektonikos” of a builder• Pieces of the lithosphere that move

around• Each plate has a name• Fit together like jigsaw puzzles• Float on top of mantle similar to ice cubes

in a bowl of water

7 - What are the two types of tectonic plates?

1)Lithosphere2) Asthenosphere

8 - What is the Lithosphere?

Lithospheric plate• The 100-km-thick surface of the Earth;

• Contains crust and part of the upper mantle;• It is rigid and brittle;• Fractures to produce earthquakes.

9 - What is the asthenosphere?

Asthenosphere:• Is the hotter upper mantle below the

lithospheric plate;• Can flow like silly putty; and• It is an elastic solid, NOT liquid!!

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10 - Different Types of Boundaries1) Transform (2) Divergent (3) Convergent

11 - Three Basic Types of Plate Boundaries

Divergent

Convergent

Transform

USGS Graphics

Using hands to show relative motion

12 - Three Basic Types of Plate Boundaries

Divergent

Convergent

Transform

USGS Graphics

13 - Divergent Boundary – Arabian and African Plates

Arabian Plate

African Plate

Red Sea

14 Divergent Boundary – Iceland

15 -Convergent Boundary – Indian and Eurasian Plates

Indian Plate

Eurasian Plate

16 - Transform Boundary – San Andreas Fault

There are a dozen large lithospheric plates (smaller plates not shown). Some plates have continents; some

don’t. All are in motion.

17 - Tectonic Plates

There are thousands of small earthquakes every day. “Strong”

earthquakes ( about magnitude of 7) occur once a month. Magnitude of over 8 occur

about once/year.

18 - Earthquakes

Notice that the earthquakes coincide with plate boundaries, and the deepest quakes

(blue) are in subduction zones.

Modified from USGS Graphics

19 - Earthquakes & Plate Boundaries

Modified from USGS Graphics

Volcanoes also tend to occur along the plate boundaries.

20 - Volcanoes & Plate Boundaries

Plates move 1-10 centimeters per year (about the rate of fingernail growth).

21 - How fast are the plates moving?

Review

• Name the 3 main layers of the Earth• What is a tectonic plate?• Name the three different types of plate

boundaries and one location on Earth for each one

Review

• Name the 3 main layers of the Earth– Crust, mantle, core

• What is a tectonic plate?– Pieces of the lithosphere that move around

• Name the three different types of plate boundaries and one location on Earth for each one– Divergent, Convergent & transform

What type of boundary is this?

What type of boundary is this?

What type of plate boundary is this?