Forces that Change the Earth’s Surface

Earth’s Systems Lithosphere(troposphere) – rocks and land Atmosphere - gases Hydrosphere – water on the ground and in the atmosphere

External Forces Weathering – The breakdown of rocks into smaller pieces. Physical Weathering – changes size and shape Ex. Frost Action Chemical Weathering – changes chemical composition Ex.Acid Rain and rusting Erosion – Transporting material from its original location Ex. Water, Wind, Gravity, Glaciers

Landforms Mountains – Formed by folding and faulting. Also by volcanic lava cooling. Plains – broad flat regions at low elevations Plateaus – layers of rock at higher elevations Built similar to mountains.

Earthquakes Earthquakes are the sudden sliding movement along a fault. The vibrations travel in waves Primary (p-waves), secondary (s-waves), and longitudinal (l-waves) P – waves travel all through the earth S – waves cannot travel through liquids like the outer core. L –waves travel on the surface

Structure of the Earth Crust – outer layer made of rock, 5-50km thick. Mantle – 2900 km thick, dense iron and magnesium rock Outer Core – 2300 km thick made of liquid iron and nickel Inner Core – 1200 km thick, made of solid iron and nickel

Plate Tectonics and Continental Drift The Earth’s crust is broken up into 12 large plates and many smaller ones. These plates slowly move and interact……mountains, earthquakes etc. A theory was proposed that they are separating. At one time they were all together as one big continent called Pangea. Evidence – ancient mountain ranges line up Continents fit like puzzles. Fossils

Pangea Plates

Sea Floor Spreading New rock is made at the center of the ocean Old rock is destroyed near the continents Ex. Mid Atlantic Ridge