ES Lesson 5 Review

Mount St. Helens is located where an oceanic plate moves toward a continental plate. What happens at these types of boundaries? Select all that apply.

• Ocean floor plates subduct beneath continental plates because they are thinner and denser, so they sink relative to the thicker less dense continental plates. Once the slab moves beneath the other plate, gravity pulls the entire slab downward into the mantle and it starts to melt.

• 1. Continental plates push the oceanic plate down because it is much more dense than the oceanic crust. The pressure from pushing the oceanic plate down causes the rock in the mountain to melt and form a volcano.

• 1. The melted rock is less dense than the surrounding rock and will rise through the upper layers forming a volcano or if in the ocean, volcanic islands. Where the two plates meet a deep canyon called a trench will form.

• When an ocean plate meets a continental plate a few things will happen. First, there will be volcanic islands developed on the ocean floor with extreme earthquakes and tsunamis. There may be some underwater moraines and canyons formed.

What are ways that plates can move in relation to other plates?  Select all that apply.

• Plates can move alongside each other

• Plates can slide on top of another plate

• Plates can move toward each other

• Plates can move away from each other

The solid rock of the cliff in this photograph is part of a continent. What is the relationship between the continent and Earth’s plates?

• The continent is part of the plate

• The continent is next to but is not part of a plate.

• The continent is on top of a layer of water that is above a plate.

• The continent is directly on top of a plate but is not part of the plate.

The Himalayan mountains are formed where two continental plates collide. What happens at these types of boundaries?

• When two continental plates collide the volcanoes are lifted up on top of new mountains which causes many earthquakes.

• When two continental plates move toward each other,  neither one moves below the other.  The plates slowly collide and crumple, forming tall mountains.

• When two continental plates collide, one subducts below the other which pushes up new mountains. The mountains start to melt because of heat and pressure and sometimes volcanoes are formed.

• When two continental plates come in contact with each other a couple of these happen. First, there are great explosions and earthquakes and then rock bubble up and eventually creates mountains.

Which is not a feature of two oceanic plates that move away from each other?

• New crust is added each time magma erupts, creating a ridge of underwater mountains.

• As the melted rock is pushed away, it takes the plate with the new crust with it like a conveyor belt.

• The rocks on the ocean floor are gradually older as you move farther away from the mid-ocean ridges.

• One crust subducts below another crust and as it subducts it melts. The melted rock rises to the surface and creates a volcano.

What happens when two plates move alongside each other?

• A volcanic mountain chain is formed.

• Tall jagged mountains are formed.

• Plates scrape against each other which causes earthquakes and destruction of buildings.

• Falling debris and rocks cause deadly avalanches

Which of the following is TRUE about when mountains have developed on Earth?

• All mountains on Earth today were present when Earth formed.

• Mountains developed for a while after Earth first formed, but no new mountains are developing today.

• 1. Mountains have been developing continuously since Earth formed, and mountains are still developing today.

• Mountains have only occasionally developed since Earth formed.