tectonic plate boundaries. plate boundaries - where the edge of two plates meet. 3 plate boundaries...
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Tectonic Plate
Boundaries
Tectonic Plate
Boundaries
Plate Boundaries - where the edge of two plates meet.Plate Boundaries - where the edge of two plates meet.
3 Plate Boundaries and 1 other1. Divergent - occurs where
plates move apart (mostly
in oceans)
2. Convergent - occurs where
plates push together
3. Transform - occurs where plates
scrape past each other
4. Hot Spots
Divergent BoundariesDivergent Boundaries
Occurs where two plates split apart
Occurs where two plates split apart
How, you ask?How, you ask?• Divergent boundaries form
when hot material rises• Heat causes crust to buldge
upward• Crust cracks and a rift valley
forms
Continued…
• Magma rises through cracked, thinned crust, forming volcanoes
• If rift valley continues widening it will sink below sea level and water from near by oceans will fill in
ex.) Red Sea
http://www.lincoln.smmusd.org/staff/Vanderveen_Web/geology/Images%20for%20notes/riftsplitscont.gif
Divergent BoundariesDivergent Boundaries
1. Mid-Ocean Ridges and Rift Valleys
A. Mid-Ocean Ridges Longest chain of mountains Most contain a rift valley along their
center EX.) Mid-Atlantic Ridge - reaches
from Iceland to Antarctica in Atlantic Ocean
B. Rift Valley
• Gap at center of Mid-ocean ridge
• Molten material rises from asthenosphere, water cools the rock until it becomes solid
http://www.harcourtschool.com/scienceglossary/images/gr6/midocean_r6.jpg
Convergent BoundariesConvergent Boundaries
Occurs where plates push together
Crust is either folded or destroyedOccurs where plates push together
Crust is either folded or destroyed
Subduction ZoneSubduction Zone
When one plate sinks below another crust melts in the asthenosphere and is
destroyed
When one plate sinks below another crust melts in the asthenosphere and is
destroyed
http://discoverourearth.org/instructor/tectonics/subduction.htmlhttp://discoverourearth.org/instructor/tectonics/subduction.html
Oceanic Crust – crust that is thin but very dense (tightly packed)
Continental Crust – crust that is thick but less dense (not tightly packed)
A. Continental-Continental Collision
A. Continental-Continental Collision
• Occurs where two continental plates
push together
• Neither plate sinks because both
plates have the same density
• Plate edges will crumple and fold,
often forming mountains
ex.) Himalayas (still forming today)
• Occurs where two continental plates
push together
• Neither plate sinks because both
plates have the same density
• Plate edges will crumple and fold,
often forming mountains
ex.) Himalayas (still forming today)
http://www.extremescience.com/graphics/Deform.gifhttp://www.extremescience.com/graphics/Deform.gif
B. Oceanic-Oceanic Subduction
B. Oceanic-Oceanic Subduction
• Occurs where one plate with oceanic
crust sinks, or subducts, under another plate with oceanic crust
• Older plate sinks because it is colder
and more dense
• When it reaches the asthenosphere it
melts in the intense heat
• Occurs where one plate with oceanic
crust sinks, or subducts, under another plate with oceanic crust
• Older plate sinks because it is colder
and more dense
• When it reaches the asthenosphere it
melts in the intense heat
2 features form at oceanic-oceanic
subductions
2 features form at oceanic-oceanic
subductions1. Deep-Ocean Trenches
- deep canyons that form in ocean floor (most found in Pacific Ocean)EX.) Pacific Plate under Philippine Plate, deepest spot is 11,000 meters into sea floor
2. Island Arcs- chains of volcanic islands that form on the
top of plates- Form parallel to deep-ocean trenches- EX.) Japan, Philippine Islands
1. Deep-Ocean Trenches- deep canyons that form in ocean floor (most
found in Pacific Ocean)EX.) Pacific Plate under Philippine Plate, deepest spot is 11,000 meters into sea floor
2. Island Arcs- chains of volcanic islands that form on the
top of plates- Form parallel to deep-ocean trenches- EX.) Japan, Philippine Islands
http://pubs.usgs.gov/publications/graphics/Fig21oceanocean.gifhttp://pubs.usgs.gov/publications/graphics/Fig21oceanocean.gif
C. Oceanic-Continental Subduction
C. Oceanic-Continental Subduction
• Occurs when ocean crust sinks under continental crust
• Oceanic sinks because it is colder and denser than continental crust
• Occurs when ocean crust sinks under continental crust
• Oceanic sinks because it is colder and denser than continental crust
1. Deep-Ocean TrenchesEx.) Pacific Plate under North American Plate (underwater earthquakes)
2. Coastal Mountains- continental crust buckles to form a range of
mountains- Mts. Parallel to deep-ocean trenches (some
form volcanoes)- Ex.) Cascade Mts. In Oregon and Washington
(Mt. St. Helen’s)
1. Deep-Ocean TrenchesEx.) Pacific Plate under North American Plate (underwater earthquakes)
2. Coastal Mountains- continental crust buckles to form a range of
mountains- Mts. Parallel to deep-ocean trenches (some
form volcanoes)- Ex.) Cascade Mts. In Oregon and Washington
(Mt. St. Helen’s)
2 features form at oceanic-continental
subductions
2 features form at oceanic-continental
subductions
http://www.rcmurphy.net/Medina%202005/images/convergent.jpghttp://www.rcmurphy.net/Medina%202005/images/convergent.jpg
http://earth.geol.ksu.edu/sgao/g100/plots/0829_10_convergent.jpghttp://earth.geol.ksu.edu/sgao/g100/plots/0829_10_convergent.jpg
Transform BoundariesTransform Boundaries
Occurs where two plates move past each other in opposite directions
Occurs where two plates move past each other in opposite directions
• As plates move, their edges
scrape and grind against each
other• Occurs mostly near mid-ocean
ridges
EX.) San Andreas Fault
• As plates move, their edges
scrape and grind against each
other• Occurs mostly near mid-ocean
ridges
EX.) San Andreas Fault
http://www.lincoln.smmusd.org http://www.lincoln.smmusd.org
Hot SpotsHot Spots
• Can be used to track plate movement• Hot spots - heated rock rises in plumes, or
thin columns, from the mantle• Volcanoes often develop above plumes• Hot spot stays in one place as tectonic
plate moves above it• EX.) Hawaiian Islands
http://earth.leeds.ac.uk/dynamicearth/plates_move/hoticon.gif