Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Crust
Document related concepts
Schiehallion experiment wikipedia , lookup
Ionospheric dynamo region wikipedia , lookup
Composition of Mars wikipedia , lookup
Post-glacial rebound wikipedia , lookup
Age of the Earth wikipedia , lookup
History of Earth wikipedia , lookup
History of geology wikipedia , lookup
Physical oceanography wikipedia , lookup
Geochemistry wikipedia , lookup
Paleostress inversion wikipedia , lookup
Plate tectonics wikipedia , lookup
Algoman orogeny wikipedia , lookup
Transcript
Chapter 9 and 10 The interior of the earth and it’s surface The Interior of the Earth z We can’t go there z Use the shock waves an earthquake makes to investigate it. z Called seismic waves z Two types – S waves (sheer waves) – P waves (pressure waves) z Measured with a seismograph Seismograph Heavy object Drum Seismograph As ground shakes the base moves but the weight stays still Seismic waves z Penetrate earth and return to surface. z Speed and direction change z S waves can’t go through liquids z P waves can, but they slow down. z As the waves go through the earth at 2900 km down, the S waves stop and the P waves slow down z At 5105 Km down the P waves speed up z What does this tell us? The Earth’s Core z The center of the earth z Two layers z Inner core – Iron and Nickel – 5000º C – Pressure keeps it solid – Responsible for magnetic field? The Earth’s Core z The outer core – Iron and Nickel – 2200º C to 5000º C – Not as much pressure so it is liquid z How do they know z P waves are pressure waves – Will go through liquid z S waves are sheer waves – won’t go through liquids S waves Liquid P waves Shadow No waves Total The Mantle z Above the outer core z 80% of the earth’s volume z 68% of the earth’s volume z Studied rocks from volcanoes z Have studied rocks from the ocean floor – Silicon, oxygen, iron, magnesium z Density increases with depth z Because there’s more iron z Measured by speed of the seismic waves The Mantle z Temperature z Has increases with depth plasticity z What is plasticity? z A solid that can flow like a liquid z Silly putty z 870º C -2200º C The Moho z the thin boundary layer between the mantle and the crust z 32-64 km z Discovered by Andrija Mohorvičić z Found seismic waves changed speed at this level z Either different composition or density. The crust z Thin outer layer we live on z If the earth were the size of an apple, the crust would be thinner than the peel z 8-32 km z Two kinds – Oceanic – Less than 10 km – all basalt- dense The crust z Continental crust – Thicker- averages 32 km, up to 70 km – Top layer granite- less dense, on top of dense basalt z Earth’s crust also called lithosphere z Lithosphere broken into large plates (called tectonic plates) 0 km Crust 32 km Moho Mantle 2900 km Outer Core 5150 km 6500km Inner Core Continent Ocean Granite Basalt Mantle Chapter 10 How the crust moves Crust Continental – – Thicker – Granite and basalt z Oceanic – Thinner – All Basalt z Stress- the pushes and pulls on the crust z causes changes in the rock – Shape – Volume z Compresses or expands z Deformation- breaking, tilting, and folding of of rocks z Stress z Three types z Compression- pushed together Stress z Three types z Compression- pushed together z Moves land higher up and deeper Stress z Tension z Pulled apart z Stretches like taffy z Thinner in the middle Stress z Tension z Pulled apart z Stretches like taffy z Thinner in the middle Stress z Shearing- pushes in two opposite horizontal directions z Rocks are torn apart or bent Stress z Shearing- pushes in two opposite horizontal directions z Rocks are torn apart or bent Stress changes z Shape z Volume z Density z Can cause cracks - fracture z Fracture along smooth surface is called a joint z Joints are parallel Faults zA break or crack where rocks move z Where earthquakes happen z Hanging wall- above the fault z Foot wall- below the fault z Three types of fault z tension causes normal fault z Compression causes reverse fault and thrust fault Normal fault z Tension pulls apart z Hanging wall moves down Foot wall Hanging wall Normal fault z Tension pulls apart z Hanging wall moves down Reverse fault z Compression pushes together z the hanging wall up Hanging wall Foot wall Reverse fault z Compression pushes together z the hanging wall up Thrust Fault z Compression continues z The hanging wall is pushed over the foot wall z end up with layers of rock repeated z Older rock on top of younger rock Thrust fault Youngest Rock Oldest Rock Lateral Fault z Caused by shear stress z Blocks move sideways Lateral Fault z Caused by shear stress z Blocks move sideways Faulted Mountains and Valleys zA series of normal faults will cause mountains to be uplifted. z Called Fault-block mountains z Sierras z Valleys will also be formed z Called rift valleys z Death Valley Fault Block Mountain Fault Block Mountain Rift valleys Rift valleys Folding z Some times rock doesn’t break z It forms folds- like wrinkles z Upward fold- anticline z Downward fold- syncline z Vary in size, from microscopic to mountain forming Anticline Syncline Why Fold z Why don’t they break z Temperature- hot rock is easier to bend z Pressure- higher pressure more likely to fold z Type of rock- some are more brittle, some are more malleable z Gradual force bends, sudden force breaks Plateau z Flat area made of layers of flat-topped rocks high above sea level z Can be formed like fault block mountains z Or by lava flows (lava plateau) z Colorado plateau- West of the Rocky mountains z formed Grand canyon z Rivers cut large plateau into several smaller ones Domes z Magma forms a bubble underneath the crust, without erupting z Half sphere surrounded by flat land z If worn into separate peaks they are called dome mountains The Crust Floats z On the mantle z Because it is less dense z The floating crust pushes down z The crust pushes up. z Balance of forces called isostasy z More material floats lower Isostasy Crust Mantle Isostasy Ice Crust Mantle Isostasy Crust Mantle Ice Isostasy Crust Mantle Over time depression will rise back up. Isostasy Sediments wash off continents Continental crust Mantle Isostasy Sediments pile up on ocean floor Continental crust Mantle Isostasy Pushes ocean floor down Continental crust Mantle
