Transcript Earth`s Crust

Plate Tectonics
Learning Goal:
Comprehend plate
tectonics and
apply in lab.
Convection
currents
Continental drift – idea that continents
have moved slowly to their current
positions due to convection currents
in the mantle.
Pangea – the idea that the all land
masses on earth were once a single
large land mass.
Ocean floor spreading – theory that
hot less dense material below Earth’s
crust rises toward the surface at the
mid-ocean ridges. Then, it flows
sideways, carrying the seafloor away
from the ridge in both directions.
http://geology.com/nsta/divergent-boundary-oceanic.gif
Convection current – unequal
distribution of heat in the mantel
causes a net movement in a circular
motion.
The Earth’s CRUST is the outer most part of
the Earth’s surface.
• Average 32 km thick (19.84 miles)
• Thickest point 70 km (in mountains)
• Thinnest point 8 km (under ocean)
Plate tectonic – theory that Earth’s crust and part
of the upper mantle are broken into sections
called plates.
Lithosphere – all of the earth’s crust and part of
the upper mantle.
http://www.allaboutspace.com/subjects/astronom
y/planets/earth/Inside.shtml
Asthenosphere – plastic like layer below the
lithosphere. The ridged plates of the lithosphere
“float” on the more plastic layer called the
asthenosphere.
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Deformation – The breaking, tilting, and
folding of crustal rock due to crustal
movement. (three types of forces)
1. Compression – squeezing of earth’s
crust that compacts the rock.
Convergent boundary
2. Tension – is the pulling apart of the
earth’s crust. Divergent boundary.
3. Shearing – pushes rocks side by
side in opposite directions.
Transform boundary.
Convergent boundary
Divergent boundary
Transformation boundary
Rift valley
subduction
FAULTS
Normal Fault (Divergent Boundary) – fault
caused by tension stress that moves the
hanging wall down relative to the foot wall.
Fault block mountain is a mountain created by
blocks of rock uplifted by normal faults.
Divergent boundary in Iceland
Reverse Fault (Convergent Boundary) –
fault caused by compression forces where
the hanging wall will move up relative to
the foot wall.
In Lateral (strike-slip) faulting
(Transform Boundary), the two blocks move
either to the left or to the right relative to one
another. Strike-slip faults are associated with
crustal shear.
San Andreas Fault, CA
Facts about folds/faults.
1. increased temp. =‘s fold
2. decreased temp =‘s fault
3. increased pressure =‘s fold
4. decreased pressure =‘s fault
5. rock type – brittle =‘s fault
6. rock type – ductile =‘s fold
7. time – greater the time =‘s fold
8. time – less time =‘s fault
Earthquakes
Earthquake – is the shaking and
trembling that results from the
sudden movement of part of the
Earth’s crust.
Tsunamis – A giant sea wave
produced by an earthquake.
Seismic Waves
Focus – The point beneath the
Earth’s surface where the rocks
break and move, the underground
origin of the earthquake.
Epicenter – The point directly
above the focus, on the earth’s
surface where the origin of an
earthquake is above ground.
Faults- Once the elastic limit of rocks is
passed, they break and move along
surfaces.
• 3 types of faults are:
• Normal Fault- These form at divergent
boundaries.
• Reverse Fault- These form at convergent
boundaries.
• Strike-Slip Fault- These form at transform
boundaries.
Seismic waves – earthquake waves. *Three
types.
1. Primary waves (P-waves) - arrive at a
given point before any other type of seismic
wave. Will pass through solid, liquid and
gas.(fastest of the three)
2. Secondary Waves (S-waves) – arrive at
a given point after the P wave. (second fastest)
Will only travel thru solids. Will NOT pass through
liquids and gases thus creating a shadow zone.
3. Surface waves (L-waves) –
slowest moving seismic
waves.
Arrives last.
Volcanoes
Volcano –A mountain that forms when
layers of lava and volcanic ash erupt
and build up.
Magma – rock that exists as a hot
liquid deep within the earth.
Lava – is magma that reaches the
Earth’s surface.
Composite Volcanoes –Violent eruptions due to
high amount of silica (D.A.N, quartz, mica,
feldspar) which is light in color and is explosive
because of large amounts of gas, ash and lava.
Domes – is the uprising area caused by magma
Shield volcano – Volcanoes composed of quiet
lava flows. The lava has a low amount of silicia
(D.A.N, quartz, mica feldspar) and is dark in color.
These volcanoes are nice with gently sloping
sides with very wide base.