The creation of fold mountains

Fold mountainsYoung fold mountains form in many parts of the world and they form along the plate margins where great Earth movements have taken place.. They are found at destructive plat

The creation of fold mountains

Learning Objective:

To learn where fold mountains are and how they are created

STARTER: How do you think these mountains have been formed?

Describe the location of fold mountains.

Fold mountains

Young fold mountains form in many parts of the world and they form along the plate margins where great Earth movements have taken place

They are found at destructive plate margins and places where there used to be destructive margins e.g the West coast of

North America

They are found where a continental and oceanic plate collide (e.g the Andes in South America were formed this way)

They form where two continental plates collide e.g the

Himalayas in Asia were formed this way

Collision boundaries occur when two plates of similar

densities move together (i.e a continental plate and a

continental plate) This causes the material between them

to buckle and rise up, forming fold mountains

The Himalayas are an example of a chain of fold

mountains They have been formed by the African plate colliding into the Eurasian plate

Collision plate boundary

Fold mountains are formed when tectonic plates collide and the plates

fold up and are forced upwards into mountains.

1) There were long periods of quiet

between Earth movements during which sedimentary rocks, thousands

of metres thick, formed in huge depressions called geosynclines 2) Rivers carried sediments and

deposited them into the depressions Over millions of years the sediments were compressed into sedimentary rocks such as sandstone and

limestone

3) These sedimentary rocks were then

forced upwards into a series of folds

by the movement of the tectonic plates Sometimes the folds were simple upfolds (anticlines) and downfolds (synclines) In such places fold were pushed over on one side, giving overfolds.

Fold mountains have been formed at times in the Earth’s

geographical history called mountain-building periods

Recent mountain-building movements have created the Alps, the Himalayas, the Rockies and the Andes, some of which are still rising For this reason many of these ranges are called

young fold mountains

http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/fold_mountains_video.shtml

fold mountains formation.wmv

Rivers deposited huge quantities of sediments in depressions called geosynclines

Over millions of years the sediments were compressed into sedimentary rocks such as sandstone and limestone

The plates moved together (a compressional boundary)

forcing the sedimentary rocks upwards into a series of folds

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Ring of Fire

San Andreas Fault

Plate Boundaries

Ocean Trenches

The majority of ocean trenches are located around the sides of the Pacific

Ocean They are associated with destructive plate margins.

The subduction zone is an ocean trench One wall is formed by subducted ocean plate (the Nazca plate), the other by the overriding continental plate (the South American plate) Ocean trenches are very deep, typically 5000-10 000 metres and narrow.

Ocean trenches are inaccessible to humans The ocean area of greatest

importance is the continental shelf, the shallow zone less than 200 metres deep off the coast The main opportunities here are for fishing and drilling for oil and gas.