Download Convergent Boundaries

Convergent
Boundaries
What happens at Convergent Boundaries?
(Continental plate – Continental plate)
• A collision boundary
(continental to continental)
is when two plates carrying
continents are welded
together to form one
continent
– Will not subduct
(go under)
– Creates folded
mountains
– Regional metamorphism
occurs here
What are Examples of a Continental Plate
converging with a continental plate
• Himalaya
mountains (India +
Asia)
• Ural Mountains
(Europe + Siberia)
• Appalachian
mountains
(N.A.+Europe) –
now split from a
spreading center
known as the midAtlantic ridge
What is a subduction zone
Boundaries?
• A subduction
zone is when an
oceanic plate
plunges beneath
another overriding
plate
• Subducting zones
create the deepest
places on the ocean
floor called deep-sea
Subduction
trenches
zone
What is a convergent Boundary?
(Oceanic-Continental)
• Oceanic crust
subducts under
continental crust
plate---MORE DENSE
PLATE GOES DOWN!
• Volcanoes form on
the continent –
volcanic arc
• Deep sea trench is
formed
What is an example of a continental
volcanic arc?
Cascade mountain range
O-C Cascade Mountains
O-C Convergent Boundary cont’d
• deep sea trench results
• mountain chain and
volcanoes form inland
on overriding plate
What happens at Convergent Boundaries
Oceanic-Oceanic crust
When two
oceanic
plates
converge:
1) Deep- sea
trench is
created
2) A chain of
volcanic
islands is
formed
-island arc
Island arc
Deep-sea
trench
What is an example of an island arc?
Japan
Convergence-Mariana Trench
• Deepest location on Earth’s
surface ~6.8mi
Farther below sea level than Mt. Everest is above it!
Hydrothermal Vents
www.ocean.udel.edu/deepsea/level-2/geology/vents
Hydrothermal Vents
Black smokers 2250m down on Juan de Fuca ridge, water exceeds 400deg C
Tube worms feeding at base of a black smoker chimney hydrothermal vent.
O-O Aleutian Islands
Aleutians seen from space
What Other Phenomena that occur
in all types of subduction zones?
•
Earthquakes occur
at greater depths
•
Lithosphere is
destroyed (it
melts)
Sliding or
Transform-fault
Boundaries
What happens at Transform-fault
Boundaries?
• Lithospheric plates
slide past each other
• Example: San
Andreas Fault
• A fault is a break in
Earths crust along
which movement has
occurred
– *shallow earthquakes
occur here
Transform Boundary
• The San Andreas Fault, California
• N. American plate
and Pacific plate
are sliding past
one another
• SW Ca. –Pacific Plate
moving NW
• Rest of U.S. is on
N. American plate
moving SE
Earthquake Trail, San Francisco area, California
Transform-San Andreas Fault
Review
What is a fault?
What happens at Transform-fault boundaries?
Are earthquakes at sliding boundaries
(transform-fault ) deep or shallow?
Plate Interactions
How are plates moving now?
How do plate interactions affect
the world?
Tectonic Plates grow and split at MidOceanic Ridges (sea floor spreading);
they melt and shrink at subduction zones
Review
Which type of crust is involved in a collision
boundary?
What feature is created there?
Which type of rock is associated with a
collision boundary?
What is an example of a collision boundary?
Review
What is a subduction zone?
Which type of crust will not subduct?
What feature are formed at a subduction
zone?
What feature is formed on the continent at
subduction boundaries?
Review
What is an example of a volcanic arc?
What type of volcanic chain is formed when
two oceanic plates converge?
What is an example of a place formed by two
oceanic plates colliding?
Where do earthquakes occur in a subduction
zone?
Review
What happens to the lithosphere in a
subduction zone?
Where are deep sea trenches on the world
today?
Locate an island arc, a volcanic arc and an
underwater volcanic chain on the world
map