Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Earth Systems 3209 Unit: 4 The Forces Within Earth Reference: Chapters 4, 15, 16, 19; Appendix A & B

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Plate Boundaries - Convergence Unit 4: Topic 2.6 Focus on...  describing and giving examples of the three types of collision boundaries.  demonstrating through a drawing the processes associated with plate convergence.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Plate Boundaries  According to the Plate tectonic theory, three boundaries exist at the edges of tectonic plates. 1)Divergent Boundary (Ridge) 2)Convergent Boundary (Trench) 3)Transform Boundary Text Reference: Pages Figure 19.17, pg. 528

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 1) Ocean – Ocean Convergent Boundary  Ocean-ocean collisions involve two oceanic plates.  Compressional forces cause the oceanic plates to move together, causing one slab of lithosphere to be consumed into the mantle initiating volcanic activity which creates volcanoes to form on the ocean floor.  The volcanoes produced at this collision boundary are island arc volcanoes; they form a curved arc on the surface (map view).  Features called ocean trenches are formed at these boundaries. Convergent Boundaries (3 Types):

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 1) Ocean – Ocean Convergent Boundary  The composition of the molten material is largely andesitic (intermediate) since the melting basaltic (mafic) oceanic crust becomes mixed with melting sediments that were located on top of the subducting plate as a result of weathering and erosion from the nearest continent (felsic).  Lithosphere is destroyed as one oceanic slab descends beneath another.  Example include the Japan island arc and the Japan trench. Convergent Boundaries (3 Types):

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 2) Ocean – Continent Convergent Boundary  Ocean-Continent collisions involve an oceanic plate and a continental plate.  Compressional forces cause an ocean plate and a continent plate to move together, due to a greater density (basaltic vs. granitic), the oceanic plate will most likely subduct beneath the continent forming a trench and subduction zone.  In a map view, a volcanic arc is created on the continent as a result of the collision.  Lithosphere is destroyed as one oceanic slab descends beneath another. Convergent Boundaries (3 Types):

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 2) Ocean – Continent Convergent Boundary  The composition of the molten material will most likely be granitic (felsic) since the upwelling magma created by the melting oceanic crust has to burn through a granitic (felsic) continent.  At depths of about 100 km the oceanic plate and parts of the mantle partially melt producing viscous magmas. This molten rock rises slowly where it cools and solidifies at depths producing plutons. However, some magma may reach the surface and erupt through composite volcanoes as violent volcanic eruptions.  Example include the Rocky mountains in North America and the Andes mountains in South America. Convergent Boundaries (3 Types):

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 3) Continent – Continent Convergent Boundary  Continent-Continent collisions involve two continental plates.  Compressional forces cause two continental plates to move together.  Once the oceanic crust between the two continents has been entirely subducted and the continental shelves have nearly joined, the process of subduction ceases.  Lithosphere is destroyed as one oceanic slab descends beneath another. Convergent Boundaries (3 Types):

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 3)Continent – Continent Convergent Boundary  Because of the low density of continental crust neither plate will subduct, both continental shelves get uplifted and deformed, forming folded mountains.  Such a collision occurred when India collided with Asia forming the Himalayan mountains and also during the formation of the Appalachian mountains  Global examples of continental-continental collisions include the Himalayan and Appalachian mountains Convergent Boundaries (3 Types):

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Plate Boundaries

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 1: Collision at which plate boundary would result in the tallest mountains? (A)ocean - ocean(C)ocean – continent (B)ocean - fault (D)continent - continent Which is associated with an oceanic to oceanic collision? (A)folded mountains(B)island arc (C)mid-oceanic ridge(D)volcanic arc

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 2: Based on the diagram below, what type of plate collision formed the Himalaya mountain range? (A) continent-continent (B) ocean-continent (C) ocean-ocean (D) seafloor-ocean

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Your Turn... Take the time and complete the following questions... (Solutions to follow) Question: A range of mountains is found on Australia’s east coast. With reference to plate boundaries, explain how this mountain range may have been formed.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Solutions... Question: A range of mountains is found on Australia’s east coast. With reference to plate boundaries, explain how this mountain range may have been formed. Answer: Mountain ranges are found along convergent plate boundaries. At these boundaries one tectonic plate moves toward and collides with another plate boundary. In the above diagram, an oceanic plate (Pacific) collides with a continental plate (Australian). This collision causes the oceanic plate to subduct beneath the continental plate. These compressional forces generally deform the tectonic plates which result in the continental plate uplifting to form a mountain chain along the length of the convergent boundary.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Extra Practice Problems: Which mountain ranges were formed by a collision between continents? (A) Andes and Rockies (B)Andes and Himalayas (C)Appalachians and Himalayas (D)Appalachians and Rockies Which feature is not associated with a convergent plate boundary? (A)deep-sea trench zone (C)mid-ocean ridge (B)earthquake (D)volcanic activity

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Summary... Overview of Points covered: 3 Types of Convergent Boundaries: 1)Ocean – Ocean 2)Ocean – Continent 3)Continent – Continent All experience;  Compressional forces  Destruction of lithosphere