MOUNTAINS

FOLDED MOUNTAINS

• Formed when rock layers are squeezed together and pushed upward.
• Usually from convergent boundaries, where plates collide.
• The Appalachian mountains form from flooding and faulting when the North American plate collided with Eurasian and African plate millions of years ago.
• Today, the highest peaks are over 3,000m tall.

VOLCANIC MOUNTAINS

• Formed when melted rock erupts onto the earths surface.
• They are located at convergent boundaries.
• They can form on land or the ocean floor.
• Most of the earths active volcanoes are concentrated around the edge of the Pacific Ocean.
• This area is known as the ring of fire.

FAULT-BLOCK MOUNTAINS

• Formed when tension makes the lithosphere break into many normal faults.
• Pieces of the lithosphere drop down compared with other pieces.
• The pieces left standing form fault-block mountains.
• The Teton mountains and the Sierra Nevadans are fault-block mountains.

THREE TYPES OF FAULTS

• Normal faults
• Reverse faults
• Strike-slip faults

NORMAL FAULTS

• These faults are called normal because the blocks move in a way that you would normally exempted as a result of gravity.
• Normal faults form when under tension.
• Tension is stress that stretches or pulls rock apart.
• Normal faults come along divergent boundaries.
• The Basin and Range area of the southwestern United States is an example.

REVERSE FAULTS

• The faults are called reverse because the hanging blocks move up, which is the reverse of what you would expect as a result of gravity.
• Reverse faults form when rocks undergo compression.
• Normal faults are common along divergent boundaries.
• Earths crust an also stretch in the middle of a tectonic plate.
• The basin and range are of the southwestern United States is a reverse fault.

STRIKE-SLIP FAULTS

• The fault blocks in strike-slip faults move past each other horizontally.
• They form when rocks are under shear stress
• Shear stress is stress that pushes rocks in parallel but opposite directions as seen in the image.
• As rocks are deformed deep in earths crust, energy builds.
• The San Andreas fault system in California is an example.

TWO KINDS OF FOLDS

• Synclines
• Anticlines

SYNCLINES