Forces that Shape the Earth

Forces that Shape the Earth

8th Grade Science ​

Continental and oceanic crust constantly changes over time due to plate tectonics. Forces at plate boundaries are strong enough to break rocks or change their shape.

Stress

Force that acts on rock to change its shape or volume, adds potential, or stored energy, to rock until it changes shape or breaks.

Multiple Choice

Force acting on a surface (such as rock) is called ......?

• density

• mass

• stress

• volume

• ​Compression

• Tension

• Shearing

Three different types of stress can occur in Earth's crust including:

Compression

Squeezes rock until it folds or breaks.

Landforms Created by Compression

• Volcanoes - an oceanic plate collides with a continental plate

• Ocean Trenches - one plate goes under another during collision forming a deep trench where the two plates meet.

• Island Arcs - two oceanic plates collide against each other

• Subduction zones - form where a more dense plate descends beneath a less dense plate

• Mountain Ranges - collision between two continental plates

Multiple Choice

Which feature will most likely form at the location marked by an X?

• a rift valley

• a transform fault

• a mountain

• a volcano

Multiple Choice

A collision between two pieces of continental crust at a converging boundary produces a ___________.

• mid ocean ridge

• rift valley

• mountain range

• volcano

Multiple Choice

What forms when denser oceanic crust is pushed under less dense oceanic crust?

• mountains

• rift valleys

• mid-ocean ridges

• island arcs

Tension

​Pulls on the crust, stretching rock so it becomes thinner in the middle.

Landforms Created by Tension:

• Mid-Ocean Ridges - tension causes oceanic crust to spread allowing hot rock from the mantle to rise creating high ridges.

• Rift Valleys - When divergent boundaries occur within a continent, they cause enormous splits in the crust.

Multiple Choice

The image shows the Mid Atlantic Ridge. Which type of boundary occurs at this ridge where the ocean floor is spreading apart? 

• convergent

• divergent

• convection

• transform

Multiple Choice

What type of stress is involved in creating the great rift valley?

• Tension

• Shearing

• Compression

• Divergent

Shearing

Pushes a mass of rock in two opposite directions.

Landforms Created by Shearing

• Fault Lines - when plates slide horizontally past each other they form a fault, or a break in the rock of the crust.

• Causes major earthquakes

Multiple Choice

What type of boundary experiences shearing stress?

• Transform

• Divergent

• Convergent

• Strike-slip

Multiple Choice

What type of stress is shown in the picture?

• compression

• tension

• shearing

Multiple Choice

What type of stress is shown in the picture?

• compression

• tension

• shearing

Multiple Choice

What type of stress is shown in the picture?

• compression

• tension

• shearing

Folding: the permanent bending of a rock exposed to extreme stress

Fault: a break in the Earth's lithosphere that occurs between two pieces of rock.

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​Ways Stress Deforms Rock

Multiple Choice

A break or crack in the Earth's crust is called a...

• plate

• fault

• fold

• rock

Multiple Choice

A bend in the Earth's crust that does not break is called a...

• plate

• fault

• fold

• rock

A break in the Earth's lithosphere that occurs between two pieces of rock.​

Faults

• Normal Fault

• Reverse Fault

• Strike Slip Fault

Three types of Faults

Convergent Boundary

Divergent Boundary

Transform Boundary

Multiple Choice

Tension stress causes _________.

• normal faults

• strike-slip faults

• reverse faults

Multiple Choice

Compression stress causes _________.

• normal faults

• strike-slip faults

• reverse faults

Multiple Choice

Shearing stress causes _________.

• normal faults

• strike-slip faults

• reverse faults

• The permanent bending of a rock exposed to extreme stress

• The rock is permanently deformed but does not break

• Caused by compression stress at a convergent boundary

• 2 types: anticline and syncline

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Folding

Multiple Choice

A downward fold in rock formed by compression in Earth's crust?

• syncline

• anticline

• rift valley

• deep ocean trench

Multiple Choice

An upward fold in rock formed by compression in Earth's crust?

• syncline

• anticline

• rift valley

• deep ocean trench