17. CONCLUSIONS
move apart
come together
slide past each other
18. 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.
20. 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
29. Practice...
The wheels on the bus go
round and round
round and round
round and round,
The wheels on the bus go
round and round
all through the town.
30. Convection Cells
The mantle of the earth
Goes round and round,
Round and round
Round and round,
The mantle of the earth
Goes round and round
All underground
31. Spreading Centers
The convection cells form
Spreading centers Rift Valley
Spreading centers
Spreading centers,
The convection cells form
Spreading centers
Creating rift valleys
32. Subduction Zones
When plates come together
One slides down, When plates come together
One slides down, One slides down,
One slides down. We call it a subduction zone.
33. Transform Fault
Plates slide past each
other at transform faults
Transform faults
Transform faults,
Plates slide past each
other at transform faults
and we live next to one!
S a n A n d r e a s F a u l t
37. 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
38. 3TYPES OF STRESS
• Tension: is the force that pulls the rocks
apart.
–Tend to become thinner.
39. 3TYPES OF STRESS
• Shearing: pushes rocks in the opposite
horizontal direction.
–Rocks can bend, twist, or break apart as they
slide past each other.
40. 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.
41. 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.
44. 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
53. 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
54. 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
63. 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 of
shield volcanoes.
64. 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.
65. 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
66. 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.
69. Summer happens when the Sun’s radiation is hitting the
Earth straight on. Earth is tilited 23.5*
Seasons have nothing to do with the Sun’s distance
from Earth.
79. “Erosion”
• a natural leveling process that wears down
high places; fills in low places
• agents: running water, ice, wind, gravity,
waves
80. “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
85. d. gully erosion
• Water cuts deeper into soil, rills coalesce
into deep troughs
• cannot (easily) be removed by tillage
• most dramatic, but most soil loss is due to
sheet and rill erosion
