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 mid-Atlantic 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 trenches

Subduction zone

What is a convergent Boundary?(Oceanic-Continental)

• Oceanic crust subducts under continental crust plate---MORE DENSEPLATE GOES DOWN!

• Volcanoes form on the continent – volcanic arc

• Deep sea trench is formed

Cascade mountain range

What is an example of a continental volcanic arc?

O-C Cascade Mountains

O-C Convergent Boundary cont’d

• deep sea trench results• mountain chain and

volcanoes form inlandon overriding plate

What happens at Convergent Boundaries

Oceanic-Oceanic crustWhen 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 plateare sliding pastone another

• SW Ca. –Pacific Platemoving NW

• Rest of U.S. is onN. American platemoving SE

Earthquake Trail, San Francisco area, California

Transform-San Andreas Fault

ReviewReview

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 Mid-Oceanic Ridges (sea floor spreading); they melt and shrink at subduction zones

ReviewReviewWhich 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?

ReviewReviewWhat 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?

ReviewReviewWhat 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