Changes to earth’s surface CHAPTER 9

Earth’s crust Earth’s surface is constantly changing Outer surface is a layer of rock called CRUST, it covers all the earth

Landforms – natural features, can be different shapes and sizes Some form quickly, some take thousands of years

weathering Weathering - the slow process of rocks in Earth’s crust being broken down into smaller pieces Water, ice, temperature changes, chemicals, and living things ALL cause weathering The two types of weathering Physical weathering Chemical weathering

Physical weathering Only SIZE of the rock is changed Larger rocks are broken into smaller pieces CAUSES WATER - carries particle of rock, soil, and sand that scrape against the rock which causes it to become smaller ICE - creates cracks that eventually split rocks TEMPERATURE - when a rock is hot is expands and becomes larger, when it is cold it contracts and becomes smaller LIVING THINGS - weeds and plants can grow in between cracks

Chemical weathering Rock is broken into smaller pieces, materials that make up the rock or soil also changes EXAMPLE Rainwater mixing with carbon dioxide makes a new chemical that breaks down the rock Animals, plants, and the activities of people all give off chemicals

Erosion Erosion – when water, ice, gravity, and wind work together to move weathered pieces of rock

Deposition pieces of rock and soil are carried by wind or flowing water Deposition - – is the laying down of pieces of Earth’s surface sometimes it happens slowly, other times very fast

As water slows, large pebbles settle first Then, smaller sand like sink Last, smallest called SILT AND CLAY sink too Deposited materials forms a fan-shaped area called a DELTA

Wind can only carry small particles In deserts, wind deposits grains of sand into mounds called SAND DUNES

Landsides No part of Earth’s surface is perfectly flat Force of GRAVITY pulls objects from a higher place to a lower place Sometimes they move slowly, sometimes rapidly Landside - the rapid downhill movement of a large amount of rock and soil

Avalanches In colder areas, and avalanche is the name for large amounts of snow and ice that fall rapidly down the mountain Strong winds, earthquakes, and explosions can trigger them Can cause a GREAT DEAL OF DAMAGE

Controlling erosion and deposition Happens when the land does not have trees and other plants People can control too! They can grow plants Farmers can plow fields into terraces Along the shore, building barriers

volcanoes Before a volcano forms things happen deep underground 50-100 miles below ground, very hot rock, called magma, is melted into liquid Gas in the magma forces it upward Volcano – forms at a weak spot in the earth’s crust when magma is forced upward and reaches the surface

Active &dormant volcanoes An ACTIVE volcano erupts frequently and shows signs of future eruptions A volcano that has not erupted for a long time is DORMAT

Began in 1983 and has continued Mt. Rainier, in Washington Has not erupted in 150 years Kileauea, in Hawaii Began in 1983 and has continued

Effects of eruptions Eruptions produce incredible amounts of rock and ash Ash can kill trees and plant life, and wild life Can cover nearby cities as well

Earth’s moving plates Earth’s outer layer is the CRUST Below, is the UPPER MANTLE These two layers are divided into very large pieces called PLATES The plates move all the time Most volcanoes are near the places where plates come together

Cause of earthquakes fault - a break or crack in rock where the earth’s crust can move Earthquake - the sudden movement that causes Earth’s crust to shake is an earthquake Focus –- is the place underground where the plates start to move and the earthquake begins Epicenter – the point on earth’s surface that is directly above the focus

Effects of earthquakes and volcanoes Earthquakes and volcanoes can affect many places on earth’s surface Ash can block the sunlight, making temperatures cooler Can cause tsunamis, or huge ocean waves Damage buildings, road, and bridges Cause major fires