Convergent Boundary
Where Crustal Plates Collide

A convergent boundary forms when two continental plates collide. Neither plate subducts because the crusts have approximately the same density. Instead, the rocks are smashed together causing them to recrystallize due to the intense heat and pressure from the colliding plates.

The rocks as they are compressed begin forming mountains above the Earth's surface. The continental crust increases in depth as the mountains grow above. The thickest crust on our planet lies beneath mountain chains formed when two continental crusts have converged.

Convergent boundary where two crustal plates collide. USGS

Formation convergent boundaries

A convergent boundary always forms when two continental plates collide. Neither plate subducts because the crust have approximately the same density. Instead, the rocks are smashed together causing them to recrystallize due to the intense heat and pressure from the colliding plates.

The rocks as they are compressed begin forming mountains above the Earth's surface. The continental crust increases in depth as the mountains grow above. The thickest crust on our planet lies beneath mountain chains formed when two continental crusts have formed a convergent boundary.

Subduction zones

Subduction zones form when an oceanic plate collides with another oceanic plate or continental plate.

The continental crust is lighter and less dense than oceanic crust. Continental crust's density is approximately 2.7 grams per cubic centimeter.

Oceanic crust is thinner and the average density is about 3.3 cubic centimeters. When the two crustal plates converge the oceanic plate always bends and subducts beneath a continental plate.

Subduction zones that occur on the coastline of Alaska are areas of frequent large and small earthquakes. The plates lock and break apart creating these earthquakes which occasionally send tsunami waves traveling across the Pacific Ocean to distant shores.

Ocean crusts collide

When two oceanic plates meet the older and colder plate like the Pacific Ocean Plate is heavier and denser. The leading edge of the plate bends and slips beneath the younger oceanic plate.

Off the island of Guam is the Mariana Trench the deepest area on our planet. In this area the leading edge of the Pacific Plate is forced beneath the smaller and lighter Mariana Plate. The trench that has formed between the two plates includes the Challenger Deep.

Convergent boundary land forms

Each of these boundaries are associated with specific land forms. Collision boundaries form great mountain chains on Earth. The European Alps and the Himalaya Range are examples of the land forms visible on Earth where continental crusts came together.

Great volcanic mountains like Mount Rainier form in a subduction zone on the continental side of a subduction zone. The Aleutian Islands in the North Pacific are an example of a volcanic island arc that has formed above a subduction zone.

More Planet Earth Information

  • Planet Earth Our home planet is unique? Find out why it is so special and such a wonderful place to live!
  • Convergent Boundary Do you know what happens when two tectonic plates form a convergent boundary?
  • Earth's Interior We can't travel to the center of the Earth so how have scientists discovered the different layers inside the Earth?
  • Asthenosphere Find out why the asthenosphere is so important and where it is located on our planet.
  • Earth's Core Find out how two scientists discovered the Earth's inner and outer core using indirect evidence.
  • Earth's LayersDo you know the different layers that make up our planet and where they are located?
  • Flood Basalts Find out about flood basalts that are great outpourings of lava that are possible causes of mass extinctions in the past.

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