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 plate boundary
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
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.
Ring of Fire
http://blip.tv/scripts/flash/blipplayer.swf?autoStart=false
&file=http://blip.tv/file/get/GatmRingOfFireKS3556.flv?source=3
San Andreas Fault
http://blip.tv/scripts/flash/blipplayer.swf?autoStart=false&file=ht
tp://blip.tv/file/get/Gatm-SanAndreasFault634.flv?source=3
Plate Boundaries
http://www.gatm.org.uk/?p=139
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.