Earth Processes Geology = the scientific study of our planet Earth

How would you describe the Earth’s Surface? How did the surface get this way?

Plate Tectonics The lithosphere is broken into 20 sections called PLATES Each PLATE is a huge slab of rock that includes the crust Fit together like a jigsaw puzzle Page 218 Plates float on layer of partly melted rock Can move 2cm – 15cm/yr

Why do they move?? CONVECTION CURRENTS cause plates to move Convection currents cause hot matter to rise while cool matter sinks MAGMA moves up and spreads out sideways in a circular pattern Magma carries the plates with it

To Review… The sections of the lithosphere are called A.Crusts B.Plates C.Puzzle pieces Convection currents cause A.Cool magma to rise and hot magma to sink B.Hot magma to rise and cool magma to sink C.The movement of the Earth’s plates D.Both B & C E.Both A & C

Plate Tectonics Changes will occur in the Earth’s crust where 2 plates meet A FAULT is a crack in the Earth’s crust along which rock moves Each plate boundary is a huge fault (226)

Faults 1.Fracture boundary = two plates sliding past each other San Andreas Fault

Faults 2. Spreading boundary – plate moving away from each other and new crust added to the surface Great Rift Valley

Faults 3. Colliding boundary = plates move toward each other = mountains Himalayas

To Review At which type of fault would the plates move into each other and cause mountains to form? At which type of fault would plates slide past one another? At which type of fault would plates move away from each other? A.Fracture boundary B.Spreading boundary C.Colliding boundary

Writing for Science Write a letter to a 2 nd grader telling them what you learned about Plate Tectonics today Must include: –What the earth’s crust is made of –What causes the plates to move –How much the plates move in a year –What a fault is

Earthquakes Plates will get caught on each other Pressure builds until rock breaks and lurches forward An earthquake is a sudden shaking or vibrating of the Earth’s crust Most occur along plate boundaries (228) Built up energy is released

Earthquakes The focus is where the first rock moves Waves move out that make the ground shake = ground rolling, shaking or lifting The Epicenter is directly above on the Earth’s surface

Earthquakes Types of Seismic Waves – –S-waves (secondary) Make rock move up and down and side to side, deep underground –P-waves (primary) Deep below the ground they stretch and squeeze the rock particles –L-waves (long) Travel along the surface Causes the most damage

Earthquakes Seismograph is the instrument records the seismic waves of energy that radiate from the focus of an earthquake Richter Scale is a series of numbers used to describe the total amount of energy released, or magnitude of an earthquake (1930) –Each increment is 10x stronger Tsunamis are caused by earthquakes under the sea that generate a powerful wave that travels to the surface

To Review Which type of wave moves along the surface of the earth during an earthquake? A.S-waves B.L-waves C.P-waves The first rock moves at the ________. A.Epicenter B.Focus

To Review What is the name of the instrument that records the seismic wave that occur during an earthquake? A.Richter Scale B.Seismograph C.Tiltmeter

Volcanoes An opening in the Earth’s surface through which magma rises Most occur at the plate boundaries and hot spots Many on the ocean floor Try to predict to save lives Tiltmeter – detects change in slope of volcano = magma might be moving

Volcanoes MAGMA VENT LAVA CRATER ASH & CINDERS

Volcanoes Eruptions depend on –Water vapor and gases in magma If escaping easily = quiet eruptions Under pressure = explosive eruption –Lava Vicious lava (thick and sticky) has gas that escapes with force and throws ash high in the air Non-viscous lava is thin and runny and lava will flow from the vent

Volcanoes At a subduction/colliding boundary 1.Sinking crust melts into magma as it enters the mantle 2.Hot magma is less dense than solid rock 3.Magma rises through openings in crust 4.Gases in magma cause pressure to build 5.When pressure is great enough – magma breaks through surface as LAVA

Volcano Types Composite = formed from alternating eruptions of cinders /ash & lava Above subduction zones Mt. Saint Helen’s

Volcanoes At a Hot Spot 1.Areas in mantle hotter than others 2.Magma has melted through the crust 3.This will form several volcanoes that will turn in to islands (Hawaii)

Volcano Types Shield = quiet eruptions that spread out in flat layers Forms a broad volcano with gently sloping sides “New real estate” Hawaiian Islands

Volcano Types Cinder cone = steep sided volcano Form from explosive eruption of lava, ash and cinders Steep with small crater Form rapidly Paricutin

To Review Quiet volcanic eruptions result from A.Water vapor and gases under tremendous pressure B.Water vapor and gases escaping easily

To Review The type of volcanoes that are created at subduction zones are A.Cinder B.Composite C.Shield

To Review The type of volcanoes that are created at areas where the mantle is hotter than the crust are A.Cinder B.Composite C.Shield

To Review When magma reaches the surface of a volcano it is called A.A crater B.A vent C.Cinder D.Lava

Soil Formation Why is soil important? Soil = mixture of weathered rock and decayed plant and animal (organic) matter formed over a long time Also includes mineral fragments, water and air Weathering = process of rock breaking into smaller and smaller fragments Humus = dark colored organic matter made of pieces of decaying plants and animals Worms mix the humus with rock fragments

Soil Profile Topsoil – –Dark –Contains humus –Worms Subsoil– –Little or no humus –Some plant roots –Minerals washed down from topsoil Bedrock – –Weathered rock –No humus –Beginning the process of becoming soil

Rock Cycle