Unique landforms occur at plate margins:
Read UG Pages 8 and 9
1.Explain the formation of ocean trenches and young fold mountains:
Rivers erode material from the land surface and transport it to the sea. The
sediment is deposited on the ocean floor and layers build up over time forming
____________rock due to compression.
Tectonic Plates move together at _____________boundaries, where two
continental plates move together.
Over ____________ of years the rocks are pushed up and down. This crumpling
produces the fold mountains, with ___________and ___________. The folding
continues even when the ocean has been removed, such as the ____________.
Fold mountains can also form at ___________boundaries where the
continental crust crumples as it meets the oceanic crust. For example where
the ____________plate meets the South American Plate to create the
____________.
At ____________ zones, the oceanic crust dives below the continental crust. At
this point, the sea is very deep and it is here that there are ocean trenches.
These are v-shaped depressions in the ocean floor that can reach depths of
10km and be thousands of km in length, but they are quite narrow at about 8km
wide.
The ________________________ in the Pacific Ocean marks where the Pacific
Plate subducts beneath the Philippine Plate.
Choose from the following…
subduction
Himalayas
Nazca
Sedimentary
anticlines
millions
destructive
Marianas Trench
2.Draw a diagram to support this explanation
Andes.
collision
synclines
3. Read this information about the uses of ocean trenches. List four benefits of
ocean trenches to people.
Ocean trenches are inaccessible to humans. The area of greatest importance is the
continental shelf which is the shallow zone less than 200 metres deep off the coast line –
here the main opportunities are for fishing and drilling for oil and gas.
At greater depths research continues – scientific research has revealed that the ocean
trenches are acting as carbon sinks so they could play a large role in regulating the earth’s
climate.
Deep sea sponges that live in the ocean trenches have been found to have properties that
could be used to treat cancers.