Slide 1

Slide 2

Plate Boundaries ~ Plate Movement ~ Plate names ~ Types of landforms/Effect of plate boundaries ~ Names of landforms Maps & Information

Slide 3

Plate Boundaries: The point at which two tectonic plates meet is called a plate boundary. It is at these locations where tectonic activity results in earthquakes, volcanoes and the formation of mountain ranges due to the movement of the plates.

Slide 4

Slide 5

This map shows 15 of the largest plates. Note that the Indo-Australian Plate may be breaking apart into the Indian and Australian plates, which are shown separately on this map.Indo-Australian Plate

Slide 6

World map showing plate boundaries (blue lines), the distribution of recent earthquakes (yellow dots) and active volcanoes (red triangles). Courtesy of NASA.

Slide 7

Slide 8

Slide 9

Slide 10

Slide 11

Slide 12

Slide 13

The diagram below shows the major plates and their boundaries. The arrows indicate the direction of movement at each plate. It is the direction of movement as well as the difference in crust which determine the variations in processes and landforms at the different plate boundaries. (animation from USGS)

Slide 14

Slide 15

Slide 16

At the edges of the plates we see the ridges and trenches that gave the first clues to Plate Tectonics. There are a few theories that control what happens along these edges, or plate boundaries as they are called. http://geography- site.co.uk/pages/physical/earth/tect.htmltheorieshttp://geography- site.co.uk/pages/physical/earth/tect.html

Slide 17

Map showing the global distribution of tectonic plates and plate boundaries. The black arrows and numbers give the direction and speed of relative motion between plates. Speed of motion is given in mm y 1. (Adapted from Bott, 1982)

Slide 18

Slide 19

Interactive Map of Plate Boundaries & Types of Boundaries Source: http://www.learner.org/interactives/dynamicearth/plate.html http://www.learner.org/interactives/dynamicearth/plate.html Use the interactive map at the weblink below to see where the three different types of plate boundaries are found throughout the world. First, find the KEY in the green box located in the lower right-hand corner of the map. Then, roll your mouse over each boundary name in the KEY to see its location.

Slide 20

Slide 21

GREAT RIFT VALLEY The red line on this map shows the eastern and western faults of the Great Rift Valley, which travels 4,500 miles from southern Africa, under the Red Sea, and into Syria in southwestern Asia. The red star is Nyiragongo volcano.

Slide 22

Slide 23

Constructive plate boundaries cause mid-ocean ridges, volcanoes and earthquakes, though often less violent than those on destructive plate boundaries. Volcanoes can form along the edges of the plate boundary due to the rising magma. These volcanoes are called shield volcanoes. Example: the North American plate moving away from the Eurasian plate formed the Mid-Atlantic Ridge and created Iceland through volcanic activity. Constructive Plate Boundaries (aka Divergent or Tensional) When two plates move away from each other creating a gap between them. Molten rock (magma) rises from the mantle to fill the gap forming a mid-ocean ridge

Slide 24

Slide 25

Slide 26

Destructive Boundary aka Convergent Movement Movement: Two plates moving towards each other (continental and oceanic crust) (note where two oceanic plates meet one will be subducted and an island arc will form) Processes: an island arc The denser oceanic crust is subducted underneath the continental crust forming a subduction zone and oceanic trench. As it is subducted it melts due to heat and pressure. The heat sources are friction between the two plates and from the earth's interior. Melting of the subducting plates creates magma which is lighter than the mantle and therefore rises resulting in the formation of volcanoes. Earthquakes also occur at this type of boundary due to the friction and pressure during subduction. Landforms Created: Fold Mountains and Ocean Trench Example: South American and Nazca Plates (forming the Andes and a deep sea trench (Peru-Chile trench)) http://geobytesgcse.blogspot.com/2007/01/plate-boundaries.html

Slide 27

Constructive Boundary aka Divergent Movement Movement: two plates moving away from each other Processes: As the two plates separate, hot magma is able to rise to fill the 'gap' creating new crust. As magma continues to build up, new mountain ranges form under the sea creating a mid-oceanic ridge. Where rising magma continues to build up above the ocean surface, a volcanic island is formed (for example Surtsey, Iceland). Both earthquakes and volcanoes occur at this type of boundary. Landforms Created: Ocean Ridge; Volcanic Islands Example: North American and Eurasian Plate - (forming the Mid- Atlantic Ridge)

Slide 28

Movement: two plates moving away from each other (animation courtesy of USGS)

Slide 29

Key Term Check Constructive Boundary (Divergent) - where two plates move away from each other resulting in new crust being formed. Destructive Boundary (Convergent) - where two plates move towards each other - in the case of a plate consisting of continental crust meeting a plate consisting of oceanic crust, the oceanic crust will be subducted and destroyed as it is less dense. Conservative Boundary - where two plates move alongside each other - although crust is neither created or destroyed here, earthquakes usually occur here. Collision Boundary - where two plates of continental crust move towards each other creating fold mountains. Volcano - a vent through which lava, ash etc. is erupted (often, but not always cone-shaped) Earthquake - a sudden ground movement

Slide 30

Collision Boundary Convergent Boundary Movement: two plates moving towards each other (both continental crust) Processes: As both plates consist of continental crust they both resist subduction and buckle and fold, being forced upwards to create fold mountains or a mountain range, such as the Himalayas. Although there is no volcanic activity at these locations, due to the forces of collision major earthquakes often occur here. Example: Indo-Australian and Eurasian Plate (forming the (Himalayas)

Slide 31

Convergent Boundary Convergent Boundary click on title for website information

Slide 32

Types of Convergent Boundary Oceanic-Continental Convergence When an oceanic plate pushes into and subducts under a continental plate, the overriding continental plate is lifted up and a mountain range is created. Even though the oceanic plate as a whole sinks smoothly and continuously into the subduction trench, the deepest part of the subducting plate breaks into smaller pieces. These smaller pieces become locked in place for long periods of time before moving suddenly and generating large earthquakes. Such earthquakes are often accompanied by uplift of the land by as much as a few meters. Oceanic-Oceanic Convergence When two oceanic plates converge one is usually subducted under the other and in the process a deep oceanic trench is formed. The Marianas Trench, for example, is a deep trench created as the result of the Phillipine Plate subducting under the Pacific Plate. Oceanic-oceanic plate convergence also results in the formation of undersea volcanoes. Over millions of years, however, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano. Such volcanoes are typically strung out in chains called island arcs. Continental-Continental Convergence When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways. The collision of India into Asia 50 million years ago caused the Eurasian Plate to crumple up and override the Indian Plate. After the collision, the slow continuous convergence of the two plates over millions of years pushed up the Himalayas and the Tibetan Plateau to their present heights. Most of this growth occurred during the past 10 million years.

Slide 33

Convergent Boundary Places where plates crash or crunch together are called convergent boundaries. Plates only move a few centimeters each year, so collisions are very slow and last millions of years. Even though plate collisions take a long time, lots of interesting things happen. For example, in the drawing above, an oceanic plate has crashed into a continental plate. Looking at this drawing of two plates colliding is like looking at a single frame in a slow- motion movie of two cars crashing into each other. Just as the front ends of cars fold and bend in a collision, so do the "front ends" of colliding plates. The edge of the continental plate in the drawing has folded into a huge mountain range, while the edge of the oceanic plate has bent downward and dug deep into the Earth. A trench has formed at the bend. All that folding and bending makes rock in both plates break and slip, causing earthquakes. As the edge of the oceanic plate digs into Earth's hot interior, some of the rock in it melts. The melted rock rises up through the continental plate, causing more earthquakes on its way up, and forming volcanic eruptions where it finally reaches the surface. An example of this type of collision is found on the west coast of South America where the oceanic Nazca Plate is crashing into the continent of South America. The crash formed the Andes Mountains, the long string of volcanoes along the mountain crest, and the deep trench off the coast in the Pacific Ocean.

Slide 34

Divergent Boundary Movement: two plates moving way from each other () Places where plates are coming apart are called divergent boundaries. As shown in the drawing above, when Earth's brittle surface layer (the lithosphere) is pulled apart, it typically breaks along parallel faults that tilt slightly outward from each other. As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, plastic interior (the asthenosphere). The sinking of the block forms a central valley called a rift. Magma (liquid rock) seeps upward to fill the cracks. In this way, new crust is formed along the boundary. Earthquakes occur along the faults, and volcanoes form where the magma reaches the surface.

Slide 35

Divergent Boundary Movement: two plates moving way from each other () Processes: Where a divergent boundary crosses the land, the rift valleys which form are typically 30-50 kilometers wide. Example 1:: include the East Africa rift in Kenya & Ethiopia, and the Rio Grande in New Mexico. Where a divergent boundary crosses the ocean floor, the rift valley is much narrower, only