Chapter 28 THE CHANGING EARTH

The Layers of Earth

The Layers of Earth Crust- a thin surface covering the Earth. 2 kinds: Oceanic & Continental What is a crack in the crust called?? Mantle- a thick molten layer between the core and the crust Outer Core- molten iron, nickel, and oxygen Inner Core- solid iron and nickel The core’s temperature ranges between 2,000 oC and 5,000 oC…hot, hot, hot!

The Surface of Earth Is there a pattern??? YES!!!

Continental Drift How is this possible? The idea that the continents were once one landmass; a “super-continent” named Pangea How is this possible?

mantle convection Heat transferred from the core to the mantle produces a slow convection of the material in the mantle Thermal Convection Demo

Sea Floor Spreading Mid-Ocean Ridges: mountain ranges on the ocean floor The closer you get to a ridge, the younger the ocean floor. Scientists concluded that the “new” land must be coming up through the ocean ridges

Plate Tectonics Earth's outer layer is made up of tectonic plates, which are moving explains the how and why behind mountains, volcanoes, and earthquakes

Plate Boundaries The area called where 2 plates meet

Divergent Plates Plates are moving apart, allowing molten material to rise up and create new crust Mid-ocean ridges Sites of earthquakes and volcanoes

Convergent Plates Occurs when two plates approach each other Subduction: one plate slides under another Often the site of volcanoes Collision can also occur between approaching plates Mountains form

Convergent Plates Subduction: Collision:

Transform Plates Occurs when 2 plates slide past each other No crust is created or destroyed Earthquakes What “famous” transform plate boundary is located in the US?

Review of Boundaries Define each term. Have the students as a class mimic the movement of divergent, convergent, and transform boundaries using their hands. Use the hyperlinks as visuals while discussing each type of plate boundary.

Fault Def. Zone of weakness or a break in the Earth’s crust. Ex. The San Andreas Fault

Earthquakes in the US: SAN ANDREAS FAULT A well known transform boundary where the Pacific plate and North American plate meet Average rate of motion across the San Andreas Fault is 2 in./yr. (3 million years L.A. will be next to S.F.)

Earthquakes in the US: OTHER FAULT LINES Do EQ’s occur anywhere else in the US? YES!...it’s been a while, but there are other fault lines in the US. New Madrid fault in Midwest 250 miles long Last major EQ in 1895 Eastern US Last major EQ in 1886 Why would an EQ be so damaging in these areas today?

Earthquakes Def. Vibrations of the earth’s crust from rock movement of plates along faults As plates move, they stretch/compress, and stress builds up When the rocks break or change shape, they release stored energy in the form of movement LIKE A RUBBER BAND! This creates seismic waves that move through Earth

Richter scale A scale (1-10) used to measure the energy given off by earthquakes. Ex. 1989 San Fransisco – 7.1 on the Richter Scale (67 deaths, 4000 injuries, and 6 Billion Dollars of damage.)

Where do Earthquakes Occur? Along plate boundaries, faults

Facts & Figures: Earthquakes Largest EQ recorded in the US: 9.2 Largest in world: 9.5 500,000 detectable EQ’s each year. More damage is caused indirectly from the EQ, not the EQ itself. 10,000 EQ’s will develop in southern California this year. However, most will not be felt Powerful EQ’s rocked the Midwest in the 1800’s. One recorded a magnitude of over 8 and caused church bells to ring in Boston Massachusetts Deadliest EQ: China in 1557, killing 830,000 people