Constructive (tensional) - Plates move apart
Destructive (collision boundary) - Plates move towards each other (Fold mountains)
Conservative - Plates slide past each other
Collision Margins - Continental plates pushing towards each other. Same density, cannot sink, so squeeze upwards making fold mountains.e.g Himalayas
Pressure - Earthquakes occur
Plates move apart - Found undea sea e.g Mid-Atlantic Ridge
- Magma rises from mantle, magma erupts to surface of Earth
- It cools + solidifies - Igneous Rock
- Eventually rock builds - Volcano
Chains of underwater volcanoes have formed along plate boundary. One may erupt out of sea to form a volcanic island e.g. Surtey and Westman Islands near Iceland
Destructive Plate Boundary
Move towards each other. Continental plate and oceanic plate. Oceanic is denser than Continental.
Oceanic plate melts due to friction + heat from mantle. Oceanic plate is forced underneath the continental - Subduction Zone
Earthquakes are triggered. Magma collects to form magma chamber, rised through cracks in contintental crust.
Plates push together, Continental crush is squashed together, forced upwards. Fold mountains.
Nazca Plate (Oceanic) ------> South American Plate (Continental Crust)
Move past each other (slide past)
No volcanoes but friction between two plates ----> EARTHQUAKES
Example - San Andreas Fault in California (Between North American Plate and Pacific Plate)
2 Continental Plates pushing towards into each other.
Same Density > cannot sink > squeeze upwards > fold mountains
Himalayas! Strong earthquakes at these margins due to pressure caused by two plates crashing into each other.
Destructive Margin (Volcanoes + Earthquakes + Fold Mountains) - Kobe Earthquake, Eruption of Mount Pinatubo
Conservative Margin (Earthquakes) - California Earthquake
Collision Margin (Fold Mountains) - Construction of the Himalayan Montains
Constructive Margin (Volcanoes and earthquakes) - Formation of iceland
Examples of plate margins
Destructive - Nazca Plate + South American Plate
Constructive - Eurasian Plate + North American Plate
Conservative - Pacific Plate + North American Plate
Volcanoes are found at plate boundaries, in narrow belts. Ring of Fire around the Pacific Ocean
Map Of Plate Margins
Formed at a Subduction Zone (Oceanic + Continental.)
Deep V shaped Trench parallel to the coast line of Nazca and South American Plate.
Formed at both Subduction and Collision Zone.
Rivers deposite huge quantities of sediments in depressions called geosynclines
Millions of years, sediments compress to sedimentary rocks (Sandstone/Limestone)
Plates move together forcing sedimentary rocks upwards into a series of folds.
Why People live on Fold Mts
Use landforms as a resource and adapt to the conditions within them.
Himalayas - Nepal, Asia
Alps - France Austria Switzerland Italy Europe
Living in Himalayas
- 80% are farmers in Nepal
- Mining - Gold, diamonds. Copper ore + Slate > Pollutes environment
- Tourism - treking/climbing/temples > money
- Living with danger - Prepared, homes built with light roofs
- Farmiing - few crops, rice & veg.
Human activity surrounding fold mountains
- Winter Sports > Skiing in resorts > Chamonix
- Climbing and Hiking in Summer
- Summer Lakeside Holidays
- Agriculture - south facing slopes (Ubac Slope)
- Forestry - coniferous forests for fuel and building.
- Communications - Roads + Railways follow valleys
- Hydroelectric power - steep slopes and glacial melt water are ideal for generating HEP - fast flowing rivers.
Composite and Shield Volcanoes
- Eruptions infrequent but often Violent
- Steep-sided Volcano
- Made of a variaty of materials
- Destructive Plate Margins
- Eruptions frequent and non-violent
- Broad volcano
- Made up of mostly lava
- Constructive Plate Margin
Named Example of Volcano
Montserrat- Caribbean Island
- Deserted towns 23 people killed
Never erupted for 370 years
Mt St Helens
Plates - North American + Pacific Plate
Date of Eruption - May 18th 1980
Facts - Triggered by 5.1 earthquake. Largest landslide speeds of 70-150 mph
Details - 57 people killed or never found. Mudflows destroyed 27 bridges, 200 homes, 185 miles of roadway,15 miles of railway, and wildlife + trees.