Transform & Divergent Boundaries

Part 1 - Transforms Boundaries

Transform Boundaries

• Plates slide past each other but are still in contact

• Creates earthquakes

• Doesn't create volcanoes or other physical features

• Currently occurring in California!

Multiple Choice

What type of motion is associated with a transform boundary?

• plates move apart

• plates come together

• plates slide past each other

Multiple Select

What type of feature(s) is/are created at a transform boundary?

• mountains

• volcanic islands

• volcanic mountains

• rift valley

• none of the choices

Transform Boundary in California

• It's called a San Andreas Fault but it is a boundary

• San Diego is sliding Northwards

Multiple Choice

The San Andreas fault in California is on this type of plate boundary.

• Convergent
• Divergent
• Transform

Boundaries aren't always neat & tidy!

• Notice at the bottom right it shows a divergent boundary

• Notice in the middle there is a transform boundary.

Multiple Choice

Which of the following shows evidence of a transform boundary?

Poll

Would you rather

• have to fart loudly every time you have a serious conversation

• have to burp after every time someone starts a conversation with you

Faults vs. Boundary

• Faults are cracks within a plate

• Plate boundaries can be called faults (kind of like misusing the term theory; usually only done with San Andreas)

• Notice faults have same 3 motions as a boundary but have different terms

• Faults can cause mountains, but not volcanoes

• I'm not requiring you to learn the 3 types of faults, just what a fault is

Multiple Choice

A fault is a crack in the earth's crust.

• True

• False

Faults in Kansas

• Kansas has more faults than this shows - but these are the bigger ones

• Remember Kansas doesn't have current plate boundaries

Earthquake Risk in U.S.

• NW U.S. - convergent boundary

• California - Transform Boundary

• Yellowstone - hot spot (magma coming up in the middle of a plate/not boundary)

• Alaska's Aleutian Islands - convergent boundary

• Remaining is due to fault activity

New Madrid Fault

• Not related to a plate boundary

• Notice Kansas would feel and be slightly affected by it

• Since midwest doesn't build for earthquakes, it would make us more prone to deaths and destruction

Multiple Choice

Which is true about the crust at a Transform Boundary?

• Crust is completely destroyed

• Crust is created

• Crust is neither completely destroyed or created

Multiple Choice

What feature is found at a transform boundary

• Rift valley

• Fault

• Seafloor spreading

• Mid-ocean ridge

Multiple Choice

What type of boundary is this?

• convergent

• divergent

• transform

Poll

Which concepts about transform boundaries are you comfortable with?

• Transform Boundary Motion

• Features Created at Transform Boundary

• Faults vs. Boundary

• Where in the U.S. do we have have a transform bounday & the name.

Divergent Boundaries

• Plates Pull Apart/Divide

• AKA Seafloor Spreading (when occurs on oceanic plate)

Thankfully the plates don't move that fast!

Plate Tectonics

• Earth's Crust is Made of 7 Large Plates & 8 Smaller Plates

• Recall the plates are actually just the pieces of the lithosphere that are getting moved about atop the asthenosphere.

• Remember there are 3 main types of motion creating the 3 main types of plate boundaries

• Today's lesson focuses more on divergent boundaries

Divergent & Convergent

• Since Earth is a sphere, if one area of Earth is pulling apart - other side is getting squished together

• So the center of the diagram shows a divergent boundary (apart/think divorce) & so on the left and right you see subduction which is what happens at a convergent boundary!

Multiple Choice

What type of plate boundary happens when two plates pull apart?

• Convergent

• Divergent

• Transform

• I'm still thinking about the caramel coming out of the Milky Way candy bar

Multiple Choice

Earth's crust is made of 1 large plate and 108 smaller plates.

• True

• False

Multiple Choice

True/False: The plates are moving about at the same rate as your finger nails grow. The plates are NOT in constant motion.

• True

• False

Divergent Boundaries on Land

• Creates Rift Valleys

• Volcanic Activity

• Earthquakes (of course)

• Currently occurring in Africa - Creating the Great Rift Valley

Great African Rift Valley

• Pulling creates the dip in the land (aka valley)

• Valley Dotted with Volcanoes

Volcanoes of Great Rift Valley

Divergent Activity in U.S.

• The arrows going apart are located on Nevada (incase you need geography help) & the divergent activity also occurs in the shaded area.

• This is NOT considered a boundary, but there is some pulling apart going on!

Multiple Choice

Plates cannot pull apart on land.

• True

• False

Multiple Choice

The Great African Rift Valley is dotted with what landform?

• volcanoes

• trenches

• beaches

• caramel coming to the earth's surface

Multiple Choice

How is a rift valley created?

• By continental plates spreading apart at a divergent boundaries

• By water moving the plates at divergent boundaries

• By oceanic plates moving apart from each other

Divergent Activity (not boundary) in U.S.

• You can see in the diagram that the crust hasn't broken apart enough to be considered a divergent boundary

• Notice that valleys and mountains can be created with this activity!

Why I'm Showing You This?!!

• Someday many of you will be taking family trips to this area - now each feature here is not caused by the divergent like activity, lots of amazing things in this area!

• Grand Canyon was created by a river carving through the rock - NOT from the divergent like activity.

• Craters of the Moon (Idaho) & Sunset Crater (AZ) are features created by this activity!

Kansas Had Some Rifting Activity!

• MANY MANY MANY years ago - rifting activity also occurred in the areas in gray (yes in Kansas!)

• It's not currently active FYI....but who knows maybe it will start again?!

Multiple Choice

In which state is there CURRENT divergent activity (not a boundary ....yet....)?

• Kansas

• Nevada

• New York

• Quebec

Rift Valley -> Ridge!

• Remember how S. America & Africa were once connected (top image)

• Initially as they pulled apart rift valleys were formed

• Eventually the valleys were below sea level & create a new water body (currently happening at the Red Sea/Africa)

• The boundary action is still continuing creating the Atlantic Ocean!

Divergent Boundaries in Oceans

• Creates Mid-Ocean Ridges

• Ridges are basically underwater mountains

• In the center (where the plates are splitting) there is volcanic activity as magma rises & creates new land!

Mid-Atlantic Ridge

• Over 10,000 Miles Long

• Iceland is located on the Mid-Atlatic Ridge (by Greenland/white in image)

• Iceland is an Example

Iceland

• Volcanic Island

• Divergent boundary is going right through the country!

• Iceland is also considered a "hot spot" as EXTRA magma comes to the surface. Most hot spots like Hawaii don't occur on a plate boundary.

Seafloor Spreading

• Pressurized Magma Rises Between Plates

• Magma Cools and Hardens Into Solid Rock

• Rock Builds Up at the Plate Boundary - Forms Underwater Volcanic Mountains

• Plates Move Out, Carrying Older Rock with It - Newer Rock at the Plate Boundary

Multiple Choice

When plates pull apart in the ocean, we call them

• mid-ocean valleys

• mid-ocean vacation homes

• mid-ocean ridges

• mid-ocean caramel

Multiple Choice

Seafloor spreading happens when two plates pull apart on the ocean floor and new rock is formed by the magma that pushes up to the surface.

• True

• False

Multiple Choice

Which island was built by the building up of new rock on the ocean floor at mid-ocean ridges?

• Hawaii

• Japan

• Jekyll Island

• Iceland

Multiple Choice

Where the seafloor is spreading, the newest rock is furthest away from the ridge.

• True

• False

Poll

Which concepts are you comfortable with below.

• Divergent boundary motion

• What's created when the continental plate splits apart and features found there

• What's created when the oceanic plate splits apart and features found there

• Where in the U.S. do we experience divergent activity (vs. boundary) & how was Iceland formed.