divergent plate boundaries

baja california

Baja California is a state in Mexico just south of California. In the Figure 1.3, Baja California is the long, skinny land mass on the left. You can see that the Pacific Ocean is growing in between Baja California and mainland Mexico. This body of water is called the Gulf of California or, more romantically, the Sea of Cortez. Baja is on the Pacific Plate and the rest of Mexico is on the North American Plate. Extension is causing the two plates to move apart and will eventually break Baja and the westernmost part of California off of North America. The Gulf of California will expand into a larger sea. Rifting has caused volcanic activity on the Baja California peninsula as seen in the Figure 1.4. Can you relate what is happening at this plate boundary to what happened when Pangaea broke apart?

plate divergence on land

A divergent plate boundary on land rips apart continents (Figure 1.2). In continental rifting, magma rises beneath the continent, causing it to become thinner, break, and ultimately split apart. New ocean crust erupts in the void, ultimately creating an ocean between continents. On either side of the ocean are now two different lithospheric plates. This is how continents split apart. These features are well displayed in the East African Rift, where rifting has begun, and in the Red Sea, where water is filling up the basin created by seafloor spreading. The Atlantic Ocean is the final stage, where rifting is now separating two plates of oceanic crust.


tectonic features of western north america

Were on a new trip now. We will start in Mexico, in the region surrounding the Gulf of California, where a divergent plate boundary is rifting Baja California and mainland Mexico apart. Then we will move up into California, where plates on both sides of a transform boundary are sliding past each other. Finally well end up off of the Pacific Northwest, where a divergent plate boundary is very near a subduction zone just offshore. In the Figure 1.1 a red bar where seafloor spreading is taking place. A long black line is a transform fault and a black line with hatch marks is a trench where subduction is taking place. Notice how one type of plate boundary transitions into another.

instructional diagrams

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___ happens at a divergent plate boundary to break up a continent.

-->  a) continental rifting

b) sea-floor spreading

c) subduction

d) a transform fault

when a continent first starts to break apart,

a) magma rises beneath the continent.

b) the continent becomes thinner.

c) the continent undergoes faulting and splits.

-->  d) all of the above.

after the continent has split a bit,

a) the crust drops down to form an ocean basin.

-->  b) a basin is created that is filled with water.

c) the process ends since the pressure has been released.

d) all of the above

the atlantic ocean has these two types of plates moving apart.

a) two continental

-->  b) two oceanic

c) one oceanic and one continental

d) none of the above

as time goes on, the gulf of california will shrink.

a) true

-->  b) false

the final stage of continental rifting is a(n) ____.

-->  a) ocean, like the atlantic

b) ocean, like the pacific

c) gulf, like the indian

d) gulf, like the sea of cortez

why is baja california splitting away from mainland mexico?

a) baja is on the north american plate and mainland mexico is on the pacific plate.

b) subduction is moving baja northward and mainland mexico southward.

-->  c) baja is on the pacific plate and mainland mexico is on the north american plate.

d) none of these

what is the relationship between continental rifting and pangaea?

a) continental rifting caused continents to come together to form pangaea.

-->  b) continental rifting tore pangaea apart into separate continents.

c) continental rifting caused the land between the continents to drop down and form the atlantic ocean basin.

d) none of these.

the red sea basin was created by

-->  a) seafloor spreading.

b) subduction.

c) transform faulting.

d) none of these.

continental rifting leads to

a) the formation of oceanic crust.

b) the stretching of the continent.

c) the formation of an ocean basin.

-->  d) all of these.

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