Plate boundaries compared

Objective: To be able to draw a diagram, describe the features and explain the

processes occurring at each plate boundary

1) Describe the distribution of plate boundaries (3 marks)2) Identify the type of plate boundary or boundaries found between:a) The African and the Eurasian plateb) The Indo Australian plate to the east of India and the Eurasian platec) The Eurasian plate and the North American plate 1 mark for each correct answer for question 2

Peer Assessment

• 1) The distribution of plate boundaries is very uneven (1 mark). However, they are often found on the edge of continents (1 mark) e.g. North and South American (1 mark) or in the middle of the ocean (1 mark) e.g. the mid Atlantic (1 mark).

• 2) (a) Destructive ( 1mark) • (b) Collision zone (1 mark) • (c) A constructive boundary (1 mark)

Plate Boundaries Compared

Conservative margin

http://whs.moodledo.co.uk/file.php/1365/EarthSystems/Earth%20Systems/Transform%20faults%20in%20California%20and%20Turkey.swf

Conservative plate boundary

Plate Boundary and Example

Explanation Earthquakes Volcanoes

Conservative

San Andreas fault- North American and Pacific plates (sliding past each other in the same direction)

•Plates slide past each other = Crust neither created or destroyed because no magma or subduction•Friction between plates = extreme stress builds in crustal rocks when released = earthquake•Longer period of movement = more stress build up so when released = more energy significant earthquake

High magnitude earthquakes

• None

http://www.youtube.com/watch?NR=1&v=t-ctk4KR-KU

f

Constructive plate boundary

Destructive plate boundary

http://www.youtube.com/watch?v=ep2_axAA9Mw&NR=1

http://whs.moodledo.co.uk/file.php/1365/EarthSystems/Earth%20Systems/Collision%20Zones.swf

Collision Zone

Tasks

• Complete the rest of the table using p14 Purple Book and p14 Green Book

Plate Boundary and Example

Explanation Earthquakes Volcanoes

Constructive

•Iceland on the mid-Atlantic ridge the Eurasian and North American plates are pulling apart

•New basaltic material rises to the surface forcing oceanic plates apart•Hot magma is able to fill the “gap” creating new crust.•As magma continues to build up new mountain ranges form under sea = mid-ocean ridge•Magma continues to rise until eventually above sea = volcanic island

• Low magnitude earthquakes maximum 6 on Richter Scale

Shield Volcanoes not very explosive or dangerousErupt basic lava and occur in fissures (cracks in the crust)

Plate Boundary and Example

Explanation Earthquakes Volcanoes

Destructive

Andes Mountains in Peru and Chiles where Nazca oceanic plate is subducted under the continental South American plate

•Oceanic crust destroyed•Oceanic plate subducts under less dense continental plate forming fold mountains in the process•Magma rises through weaknesses melting crust forming volcanoes

The highest magnitude earthquakes recorded occur here

Very explosive and dangerous volcanoes with steep sides called composite cone volcanoesErupt andesitic lava

Plate boundary and Example

•Processes Earthquakes Volcanoes

Collision Zone

Himalayas Indian and Eurasian continental plate crash into each other

•Two continental plates moving towards each other•Same density so no subduction occurs this cause the crust to buckle and fold creating fold mountains• No volcanoes occur here as subduction does not occur•Crust neither formed or destroyed

Very high magnitude earthquakes

None because no material is subducted