tectonic plate boundaries. plate boundaries - where the edge of two plates meet. 3 plate boundaries...

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