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Chapter 9 and 10 The interior of the earth and its surface.

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Presentation on theme: "Chapter 9 and 10 The interior of the earth and its surface."— Presentation transcript:

1 Chapter 9 and 10 The interior of the earth and its surface

2 The Interior of the Earth l We cant go there l Use the shock waves an earthquake makes to investigate it. l Called seismic waves l Two types – S waves (sheer waves) – P waves (pressure waves) l Measured with a seismograph

3 Seismograph Heavy object Drum

4 Seismograph As ground shakes the base moves but the weight stays still

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7 Seismic waves l Penetrate earth and return to surface. l Speed and direction change l S waves cant go through liquids l P waves can, but they slow down. l As the waves go through the earth at 2900 km down, the S waves stop and the P waves slow down l At 5105 Km down the P waves speed up l What does this tell us?

8 The Earths Core l The center of the earth l Two layers l Inner core – Iron and Nickel – 5000º C – Pressure keeps it solid – Responsible for magnetic field?

9 The Earths Core l The outer core – Iron and Nickel – 2200º C to 5000º C – Not as much pressure so it is liquid l How do they know l P waves are pressure waves – Will go through liquid l S waves are sheer waves – wont go through liquids

10 S waves Liquid

11 P waves

12 Total Shadow No waves

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14 The Mantle l Above the outer core l 80% of the earths volume l 68% of the earths volume l Studied rocks from volcanoes l Have studied rocks from the ocean floor – Silicon, oxygen, iron, magnesium l Density increases with depth l Because theres more iron l Measured by speed of the seismic waves

15 The Mantle l Temperature increases with depth l Has plasticity l What is plasticity? l A solid that can flow like a liquid l Silly putty l 870º C -2200º C

16 The Moho l the thin boundary layer between the mantle and the crust l km l Discovered by Andrija Mohorvičić l Found seismic waves changed speed at this level l Either different composition or density.

17 The crust l Thin outer layer we live on l If the earth were the size of an apple, the crust would be thinner than the peel l 8-32 km l Two kinds – Oceanic – Less than 10 km – all basalt- dense

18 The crust l Continental crust – Thicker- averages 32 km, up to 70 km – Top layer granite- less dense, on top of dense basalt l Earths crust also called lithosphere l Lithosphere broken into large plates (called tectonic plates)

19 Inner Core Outer Core Mantle Moho Crust 6500km 5150 km 2900 km 32 km 0 km

20 Mantle Basalt Granite Continent Ocean

21 Chapter 10 How the crust moves

22 Crust l Continental – – Thicker – Granite and basalt l Oceanic – Thinner – All Basalt l Stress- the pushes and pulls on the crust l causes changes in the rock – Shape – Volume l Compresses or expands l Deformation- breaking, tilting, and folding of of rocks

23 Stress l Three types l Compression- pushed together

24 l Three types l Compression- pushed together l Moves land higher up and deeper Stress

25 l Tension l Pulled apart l Stretches like taffy l Thinner in the middle

26 l Tension l Pulled apart l Stretches like taffy l Thinner in the middle Stress

27 l Shearing- pushes in two opposite horizontal directions l Rocks are torn apart or bent

28 Stress l Shearing- pushes in two opposite horizontal directions l Rocks are torn apart or bent

29 Stress changes l Shape l Volume l Density l Can cause cracks - fracture l Fracture along smooth surface is called a joint l Joints are parallel

30 Faults l A break or crack where rocks move l Where earthquakes happen l Hanging wall- above the fault l Foot wall- below the fault l Three types of fault l tension causes normal fault l Compression causes reverse fault and thrust fault

31 Normal fault l Tension pulls apart l Hanging wall moves down Hanging wall Foot wall

32 Normal fault l Tension pulls apart l Hanging wall moves down

33 Reverse fault l Compression pushes together l the hanging wall up Hanging wall Foot wall

34 Reverse fault l Compression pushes together l the hanging wall up

35 Thrust Fault l Compression continues l The hanging wall is pushed over the foot wall l end up with layers of rock repeated l Older rock on top of younger rock

36 Thrust fault Oldest Rock Youngest Rock

37 Lateral Fault l Caused by shear stress l Blocks move sideways

38 Lateral Fault l Caused by shear stress l Blocks move sideways

39 Faulted Mountains and Valleys l A series of normal faults will cause mountains to be uplifted. l Called Fault-block mountains l Sierras l Valleys will also be formed l Called rift valleys l Death Valley

40 Fault Block Mountain

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42 Rift valleys

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44 Folding l Some times rock doesnt break l It forms folds- like wrinkles l Upward fold- anticline l Downward fold- syncline l Vary in size, from microscopic to mountain forming

45 Anticline Syncline

46 Why Fold l Why dont they break l Temperature- hot rock is easier to bend l Pressure- higher pressure more likely to fold l Type of rock- some are more brittle, some are more malleable l Gradual force bends, sudden force breaks

47 Plateau l Flat area made of layers of flat-topped rocks high above sea level l Can be formed like fault block mountains l Or by lava flows (lava plateau) l Colorado plateau- West of the Rocky mountains l formed Grand canyon l Rivers cut large plateau into several smaller ones

48 Domes l Magma forms a bubble underneath the crust, without erupting l Half sphere surrounded by flat land l If worn into separate peaks they are called dome mountains

49 The Crust Floats l On the mantle l Because it is less dense l The floating crust pushes down l The crust pushes up. l Balance of forces called isostasy l More material floats lower

50 Isostasy Mantle Crust

51 Ice Isostasy Mantle Crust

52 Ice Isostasy Mantle Crust

53 Isostasy Mantle Crust Over time depression will rise back up.

54 Isostasy Continental crust Mantle Sediments wash off continents

55 Isostasy Continental crust Mantle Sediments pile up on ocean floor

56 Isostasy Continental crust Mantle Pushes ocean floor down


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