Mountain Building

Mountain Building

 Mountain ranges form wherever tectonic plates collide.

 Where oceanic crust subducts under continental crust, magma deforms the continental crust forming mountains and volcanoes.

 Where two continental tectonic plates collide, the plates buckle like car hoods in a crash, forming vast mountain ranges.

Faults

 Faults are breaks or cracks in the Earth’s crust along which movement has occurred.

 The surface that separates two moving pieces of crust is called the fault plane.

Three types of Faults:

 Normal: rocks on one side of fault plane drop down below rocks on the other side.

 Reverse: rocks on one side are driven up over the other side.

 Strike-slip: rocks on opposite sides of fault plane move horizontally past each other.

Folds

 During plate collisions, rock layers along continental margins sometimes crumple into folds:

 Anticlines: upfolds in the rock layers

 Synclines: downfolds in the rock layers

Uplifting

 At some plate boundaries, sedimentary layers are raised to high levels with little deformation – end up with aquatic fossils and beaches at high elevations.

Tilting/Overturning

 Most sedimentary rocks are formed in level layers

 Folding and uplifting may result in layers being tilted

 Sometimes rocks are tilted over on themselves and end up upside-down – “overturned”.