Science c9 L1

Chapter 9

Plate movement

HW TIME

Read Pages 237-243

Questions 1&2

Transform Fault Boundaries

Continental Plate Converging

with Continental Plate

A Canadian geophysicist, J. Tuzo Wilson, discovered a new kind of plate boundary, which he called a fault.

Oceanic Plate Converging with Oceanic Plate

Oceanic Plate Converging with Continental Plate

Convergent Boundaries

Divergent Boundaries

Unlike the other converging plates, when two continental plates meet there is no subduction.

Convergent Boundaries

Divergent Boundaries

A fault is an area where rocks are being broken by movement in the crust.

On land, divergent boundaries create valleys called rifts.

When two oceanic plates collide, one plate sinks below the other and deep trenches are formed.

Instead the crust buckles and crumbles, pushing up and creating mountains or areas of high level ground called plateaus.

The landforms created at a convergent boundary depend on what type of collision is occuring.

Wilson also discovered that divergent and convergent plate boundaries could suddenly stop and "transform into faults. Therefore the zone between plates that are slipping past each other are called

When an oceanic plate collides with a continental plate, the oceanic plate is subducted under the continental plate.

As divergent boundaries are constantly spreading the Earth apart and creating new crust, and the Earth's size has not changed significantly, old crust must be destroyed, or recycled, at the same rate.

transform plate boundaries

There are 3 types of plate boundaries

Challenger deep, a section of the Mariana Trench is so deep that even Mount Everest could not fill it.

Boundaries of plates that are moving apart

On the ocean floor this is known as sea-floor spreading

As plates separate, hot molten magma rises to Earth's surface to form new crust.As magma meets the water, it cools and solidifies, adding to the edges of the sideways-moving plates. As magma piles up along the crack, a long chain of mountains forms gradually on the ocean floor. This chain is called an oceanic ridge.

An example of a ridge, is the Mid-Atlantic Ridge, which runs along the middle of the Atlantic Ocean and is the boundary that is separating the Eurasian and North American Plate.

Most transform fault boundaries are found on the ocean floor. Shallow earthquakes are very common along transform fault boundaries.

This recycling takes place at convergent boundaries where plates are crashing into one another very slowly. Overtime, these collisions lead to one plate sinking below the other. These areas are known as

An oceanic plate converging with a continental plate

This creates deep ocean trenches along the edge of a continent

Subduction Zones.

Just like countries have borders that mark their area, plates also have borders.

We call these borders, plate boundaries

Note: Subduction and mountain formation does not occur at transform plate boundaries.

Two oceanic plates converging

The collision of an oceanic plate and continental plate not only causes the oceanic plate to subdue, but it causes the continental plate to be pushed up, and thus creating a mountain.

Two continetal plates converging.

These rifts are similar to those that would be seen in sourdough bread.

• As the bread is heated and expands, the crust will expand and create ridges.

Subduction can be seen as nature's way of recycling the Earth's crust.

As you can imagine, the formation of the new crust on either side of the vents would act to push plates apart, as we see at the Mid-Atlantic Ridge, which helps to move North America and Europe further and further apart

The areas where plates meet are called plate boundaries

Divergent Boundaries

Convergent Boundaries

Transform

fault

boundaries