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1.4 OUtline Plates converge or scrape past each other.

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Presentation on theme: "1.4 OUtline Plates converge or scrape past each other."— Presentation transcript:

1 1.4 OUtline Plates converge or scrape past each other

2 I. Tectonic plates push together at convergent boundaries  Subduction: when one oceanic plate sinks beneath another  Continental-continental collision  Continental-continental collision: occurs when 2 plates carrying continental crust push together  Both crusts are the same density, neither plate can sink beneath the other  European Alps are found where the African & European plates are colliding  Himalayas first formed when the Indian plate began colliding with the European Plate

3 B. Oceanic-Oceanic Subduction  Oceanic-oceanic subduction: occurs when 1 plate with oceanic crust sinks under another plate with oceanic crust  Two main features form at oceanic-oceanic subductions:  Deep-Ocean Trenches – most are found in the Pacific Ocean; for example at the Mariana Trench the Pacific Plate is sinking under the Philippine Plate  Island Arcs – there are chains of volcanic islands that form on the top plate, parallel to a deep ocean trench; as oceanic crust of the sinking plate melts, magma rises through the top plate Examples: Philippine Islands, Aleutian Islands

4 C. Oceanic-continental subduction  Oceanic-continental subduction: occurs when ocean crust sinks under continental crust  Deep-ocean trenches and coastal mountains form at these boundaries  Deep-Ocean Trenches – some of the world’s youngest trenches are in the eastern Pacific Ocean; for example, the Pacific Plate is sinking under the North American Plate causing underwater earthquakes  Coastal Mountains – continental crust buckles to form mountain ranges; parallel to a deep-ocean trench; some are active volcanoes

5 II. Tectonic plates scrape past each other at transform boundaries  At a transform boundary, crust is neither formed nor destroyed  As the plates move, their edges scrape & grind against each other  Transform boundaries occur mostly on the sea floor near mid-ocean ridges  They also occur on land; example: San Andreas Fault

6 III. The theory of plate tectonics helps geologists today  Theory has helped to explain Earth’s past and to predict what might happen along plate boundaries in the future  Theory of plate tectonics gives scientists a way to study & predict geologic events

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