Chapter 8 Lesson 1 What are Earth’s layers made of? Landforms: a feature of the land on Earth Ex) desert, mountain, canyon, valley, plain Ridge: long rows of towering mountains Trenches: long, narrow canyons on the ocean floor

Earth’s Layers Atmosphere: above the Earth’s surface, thin layer of gases in the air. Lithosphere: solid part of the Earth’s surface(crust and upper mantle) Hydrosphere: part of the Earth with water

CRUST: the outermost solid layer of Earth (thin shell) that we live on. MANTLE: the most massive part of the Earth. Outer Mantle: is solid like the crust Inner Mantle: is so hot the rock softens and can flow very slowly CORE: innermost, very dense layer (center) of the Earth Outer Core: is so hot it is liquid iron and nickel Inner Core:is even hotter but because of the pressure it’s solid iron/nickel

Earth’s Plates: The lithosphere is broken into pieces of Earth called plates. These plates have different shapes and sizes. All the plates fit together to cover the Earth (like a jigsaw puzzle) Some plates are made up of both continental crust and oceanic crust. These large plates of lithosphere ‘float’ on top of the lower mantle.

Lesson 2 How do Earth’s plates help create landforms? Alfred Wegener believed that 225 million years ago the continents were joined together. (Pangaea) He believed continental drift caused the continents to move apart.

Wegener’s evidence: (1) plant and animal fossils found on the coast of South America matched where it would have connected with Africa. (2)Rock layers along the coast of South America match those with Africa. What he couldn’t prove is what caused the continents to actually move.

Seafloor Spreading: 2 plates move apart slowly and allow magma to flow up and harden into new crust. Convection (the force that moves Earth’s plates) was the missing piece to Wegener’s proof. Earth’s magnetism ‘flips’ about every half million years and is trapped in the rocks below.

Lesson 3 How Scientists Explain Earth’s Features Plate Tectonics: Earth’s lithosphere is broken into about 20 large moving plates of land. Plate boundaries are the borders where the plates meet. The break in the lithosphere where the plates meet is called a fault.

Spreading Boundary: Plates move away from each other and let magma seep up into the gap and harden into new crust. Colliding Boundary: Plates push towards each other making the land rise. (forming mountains)

Fracture Boundary: two plates slide past each other in opposite directions (causes earthquakes). The break in the crust between the plates is a FAULT.

Lesson 4 What Causes Earthquakes and Volcanoes? Earthquakes: plates sometimes get stuck on jagged rock edges that stop it from moving. Pressure builds up over time until the rock breaks and the plate moves suddenly. FOCUS: the place underground where the rock actually breaks free. EPICENTER: point on Earth’s surface directly above the focus. During an earthquake the energy waves spread out from the focus.

Earthquake Magnitude measures the strength of the energy released during the earthquake. The closer to the epicenter the waves are strongest and the most damage will occur. The Richter scale is used to measure the magnitude of earthquakes. A 4 on the Richter scale is 31 times more powerful than a 3 on the Richter scale.

VOLCANOES: occur usually near a plate boundary where magma rises from the lower mantle. Pressure can build up in a volcano as one plate is pushed under another plate. Eventually pressure will cause an eruption.