Layers of the Earth Chapter 8 Section 1

Landforms Plateau- raised, flat land Gorge- deep crack in the plateau Mountains- Plains- flatlands with very few trees Valleys- the land between two mountains Many landforms are hidden by water.

Earth’s layers Atmosphere- the gases that we breathe, weather occurs here, and it acts as an insulator protecting Earth Crust- Outermost solid layer Thickness varies Continental crust- soil and rocks we live on- 35-40 km Oceanic Crust- soil and rocks underneath the water- 6-11 km Thinnest layer Mantle-Below the crust Thickest part of Earth Outer portion is solid like the crust and the inner portion is so hot that the rock can flow like a liquid

Earth’s layers Core- Divided into the inner and outer core Temperature s about 7,000 degrees Celsius Outer core is liquid Inner core is solid

Earth’s Crust 46.6 % is oxygen 27.7 % is silicon The other elements are aluminum, iron, calcium, sodium, potassium, magnesium and trace other elements

Earth’s plates Lithosphere- the crust and the upper mantle The lithosphere is broken into plates There are about 20 tectonic plates that are all different sizes and shapes They may be made of continental and oceanic crust

How does Earth plates help shape Landforms Chapter 8 Section 2

Continental Drift In 1912, Alfred Wegener suggested a reason for why the coastlines of certain continents looked like they fit together at one time. He felt that the continents were all joined about 225 million years ago. He called this Super continent- Pangaea- meaning all Earth

Continental Drift Wegener thought all the continents were joined at one time and slowly drifted apart. Proof for the Continental Drift Theory The coastlines fit together like puzzle pieces Plant and animal fossils found on West Coast of Africa matched those found on the East Coast of South America Rock layers on W coast of Africa matched rock layers on E. coast South America

Problems Wegener could not explain what forces moved the continents apart. It was not until much later that scientist figured out the forces pulling the continents apart. They had to look to the seafloor.

Seafloor Spreading Harry Hess- 1960 He noticed that new seafloor forms at ocean ridges. The magma rises and forms a ridge which pushes the old seafloor away The magma rises when the plates pull apart

Convection current Arthur Holmes- 1930’s He noticed that when you heat liquids the particles move faster and the hot liquid rises. The hot liquid will eventually cool and sink down This process of heating and cooling is a convection current. Convection currents move the plates because the molten rock in the mantle rises then cools.

Final Proof of Continental Drift Scientists studied the magnetism of the rocks near the Mid ocean Ridge They saw that in some places the magnetism faced north while in some places it faced south. Every half-million years the pattern flips. This proves that old rock is pushed from the newly formed rock at the Mid- ocean ridge

How do scientist explain Earth’s Features Chapter 8 Lesson 3

Theory of Plate tectonics Earth’s lithosphere is broken into 20 plates The continents and the ocean floor make up the surfaces of the moving plates The plates can move in one of 3 ways Toward one and another Away from one and another Sliding past each other The plates move about 2 cm each year

50 million years from now The plates will have begun to move back together Another Pangaea like continent is expected

Plate boundaries A plate boundary is the area where two plates form. A spreading boundary- where two plates move apart Huge valleys can form Responsible for sea floor spreading Caused the Mid- Atlantic Ridge

Fracture Boundaries At a fracture boundary- the plate slides past each other A fault- a break in the Earth’s crust is made Responsible for strong earthquakes

Colliding boundaries Colliding boundaries occur when two plates push against each other. 1. One plate could slide beneath another- subduction zone and volcanoes occur 2. The two plates collide making mountains It is also possible to have earthquakes and ocean trenches at this boundary

What Causes earthquakes and volcanoes Chapter 8 Section 4

Earthquakes Plate movement occurs slowly so you can’t see or feel it. The rocks jagged edges catch and pressure builds up If the pressure is too strong then an earthquake happens

Earthquakes The point underground of an earthquake is the FOCUS The point directly above the focus on Earth’s surface is the EPICENTER The energy of an earthquake is carried in waves The waves can move up or down The waves can move back and forth The waves can roll or move in a circular fashion

Earthquake magnitude The greatest damage occurs near the focus and epicenter As the waves move out- they lose energy Almost all the largest earthquakes have occurred in California and Alaska The boundary between the Pacific Plate and the North American plate

Richter Scale The magnitude of an earthquake is measured on the Richter scale Each increase of 1 on the Richter scale means a 31 times more energy is released

Volcanoes A volcano- an opening in the surface of one of Earth’s plates through which magma rises. Ash cloud- tiny bits of rock spew out the opening Crater- steep-sided depression at the top of a volcano Caldera-crater that is at least 1.6 km wide

Volcanoes Most often occur when one plate sinks beneath another Most volcanoes occur on the ocean floor

Detecting an Earthquake or volcano Seismometers- detect shaking or tremors in Earth’s crust Magma rising or Earth’s plates moving Tiltmeter- detects changes in the slope of the land Seismograph- records the movement or tremors at faults