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CONCLUSIONS move apart come together slide past each other
Divergent Boundaries• Plates are moving apart from each other• We also term these sites spreading centers.• Form what is known as a rift valley. It is at divergent plate boundaries where new crust is created.
Convergent Boundaries• Plates are pushing into neighboring plates.• Usually a subduction zone occurs. That is when oceanic crust crashes into and slides under continental crust.• 3 convergent boundaries can occur: –continental/oceanic crust collision –oceanic/oceanic collision –continental/continental collision
3TYPES OF STRESS• Compression: occurs when crustal rocks are squeezed together. –Often times reduces volume of rock –Will push rock higher up or deeper down into the crust
3TYPES OF STRESS• Tension: is the force that pulls the rocks apart. –Tend to become thinner.
3TYPES OF STRESS• Shearing: pushes rocks in the opposite horizontal direction. –Rocks can bend, twist, or break apart as they slide past each other.
The Results of Stress• High pressure and temperatures caused by stress in the crust generally deform rocks.• When stress is applied slowly, the deformed rock will return to it’s original shape.• In extreme stress, rock becomes so deformed it may break.
FOLDING• When rocks respond to stress by becoming permanently deformed without breaking it is called folding. –Folds vary in size –There are 3 general types of folds.
TYPES OF FAULTS• Normal fault: hanging wall moves down relative to the footwall along divergent boundary• Reverse fault: compression causes the hanging wall to move up relative to the footwall• Thrust fault: fault plane is a low angle or nearly horizontal & hanging wall is pushed up over rock• Strike-slip fault: rock on either side of the fault plane slides horizontally at transform boundaries
P Waves–Primary Waves (P waves): move fastest and are recorded first • Can travel through solid & liquid • Compression waves- cause the rock particles to move together & apart along the wave direction
S Waves– Secondary Waves (S waves): second to be recorded • Travel only through solid material: cannot be detected on the side of the earth opposite the epicenter…Why? Can’t go through the liquid of the earth’s outer core! • Shear waves- cause rock particles to move at right angles to the wave direction 53
Volcanic Rock Fragments• Volcanic ash • Volcanic dust – Particles less than 2mm – Particles less than .25 mm
Volcanic Rock Fragments• Lapilli • Volcanic bomb – Particles less than 64mm – Round or spindle shape
Volcanic Rock Fragments• Volcanic Blocks –Largest pyroclastic material, can be as big as a house!
Shield Volcano• Covers a wide area• Generally results from lava eruption• Layers of hot mafic lava flow out around the vent, harden, and slowly build up to form a cone.• The Hawaiian Islands are a chain ofshield volcanoes.
Cinder Cone• Made up of solid fragments ejected from the volcano.• Most cinder cones have very steep slopes, often close to 40 degrees.• Rarely more than a few hundred meters high.
Strato / Composite Volcano• Many volcanoes have both quiet and explosive eruptions.• Composite volcanoes are formed as a result of alternating layers of lava and pyroclastic material.• Also known as stratovolcanoes
Craters/ Calderas• A crater is a funnel-shaped pit at the top of the volcanic vent .• Formed when material is blown out of the volcano by explosion.• Calderas are formed when slippage or sinking occurs in the crater.
Soil ParticlesLoam--equal mixture of sand, silt, clay, and humus.
“Erosion”• a natural leveling process that wears down high places; fills in low places• agents: running water, ice, wind, gravity, waves
“accelerated erosion”• Process by which soil particles are removed, transported and deposited; rate of removal of soil greater than rate of formation • 500 yrs / inch topsoil –Caused by removal of vegetation • agents: wind, water