The interior of the earth and it’s surface Chapter 9 and 10 The interior of the earth and it’s surface

The Interior of the Earth We can’t go there Use the shock waves an earthquake makes to investigate it. Called seismic waves Two types S waves (sheer waves) P waves (pressure waves) Measured with a seismograph

Seismograph Heavy object Drum

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

Seismic waves Penetrate earth and return to surface. Speed and direction change S waves can’t go through liquids P waves can, but they slow down. As the waves go through the earth at 2900 km down, the S waves stop and the P waves slow down At 5105 Km down the P waves speed up What does this tell us?

The Earth’s Core The center of the earth Two layers Inner core Iron and Nickel 5000º C Pressure keeps it solid Responsible for magnetic field?

The Earth’s Core The outer core Iron and Nickel 2200º C to 5000º C Not as much pressure so it is liquid How do they know P waves are pressure waves Will go through liquid S waves are sheer waves won’t go through liquids

S waves Liquid

P waves

Total Shadow No waves

The Mantle Above the outer core 80% of the earth’s volume Studied rocks from volcanoes Have studied rocks from the ocean floor Silicon, oxygen, iron, magnesium Density increases with depth Because there’s more iron Measured by speed of the seismic waves

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

The Moho the thin boundary layer between the mantle and the crust 32-64 km Discovered by Andrija Mohorvičić Found seismic waves changed speed at this level Either different composition or density.

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

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

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

Continent Ocean Granite Basalt Mantle

Chapter 10 How the crust moves

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

Stress Three types Compression- pushed together

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

Stress Tension Pulled apart Stretches like taffy Thinner in the middle

Stress Tension Pulled apart Stretches like taffy Thinner in the middle

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

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

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

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

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

Normal fault Tension pulls apart Hanging wall moves down

Reverse fault Compression pushes together the hanging wall up Foot wall

Reverse fault Compression pushes together the hanging wall up

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

Thrust fault Youngest Rock Oldest Rock

Lateral Fault Caused by shear stress Blocks move sideways

Lateral Fault Caused by shear stress Blocks move sideways

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

Fault Block Mountain

Fault Block Mountain

Rift valleys

Rift valleys

Folding Some times rock doesn’t break It forms folds- like wrinkles Upward fold- anticline Downward fold- syncline Vary in size, from microscopic to mountain forming

Anticline Syncline

Why Fold Why don’t they break Temperature- hot rock is easier to bend Pressure- higher pressure more likely to fold Type of rock- some are more brittle, some are more malleable Gradual force bends, sudden force breaks

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

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

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

Isostasy Crust Mantle

Isostasy Ice Crust Mantle

Isostasy Ice Crust Mantle

Over time depression will rise back up. 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