Convergent Boundaries

Earth’s outer layer comprises of massive pieces of solid rock. These pieces are known as tectonic plates and are constantly moving.  Sometimes two tectonic plates crash into one another while moving. These form convergent boundaries. Other times, plates will move away from one another. This is known as a divergent boundary.

Mountains form at convergent boundaries.

Types of Convergent Boundaries

Oceanic Crust and Continental Crust

Sometimes an oceanic crust and continental crust collide. This is one type of convergent boundary.  Oceanic crust makes up oceans and the continental crust makes up land.  When these two crusts collide, the oceanic crust is forced to move downwards because of its high density.  Whereas, the continental crust pushes upward because it is lower in density.
The oceanic crust pushes further and further into Earth’s mantle.  As this occurs, the temperature of the crust increases. At around 100 km, the oceanic crust will begin melting. This process is known as subductionIn fact, subduction can cause friction between plates.  This friction can produce tsunamis and earthquakes. Also, subduction can lead to the formation of volcanoes.

During subduction, denser oceanic crust plate descends into the upper mantle. There, it begins to melt.

Two Continents

When two continents crash into one another, it forms mountains.  The interaction is quite simple.  However, in this scenario, both continents have similar densities. Sometimes subduction occurs. But, the most common result caused by the collision of the two continents is a mountain range.
Scenic vista of mountains.

Two converging continents can create mountains.

Two Pieces of Oceanic Crust

When two pieces of oceanic crust collide, there will be a subduction zone.  The older crust will move underneath the younger crust since it has a higher density. The older crust will subduct into the mantle and begin to melt. However, this may lead to magma chambers, which are large pools of melted rock beneath the Earth’s surface.  Sometimes, collisions between two pieces of oceanic crust lead to earthquakes and volcanoes.
Night shot of Tungurahua volcano

The Tungurahua Volcano in Ecuador is a highly active volcano. It is the result of a convergent boundary between two pieces of oceanic crust.

Real-Life Convergent Boundaries

  1. The Pacific Plate and the North American plate form a convergent boundary. This has led to the formation of an oceanic trench, known as the Aleutian Trench.  It has also formed a series of volcanic islands, known as the Aleutian Islands.
  2. Sometimes when plates collide they form mountains. A great example of this is the Pontic Mountains in Turkey.  They were created by a collision between the Eurasian Plate and African Plate.
  3. Subduction created the Mariana Trench.  In fact, this trench is the deepest point on Earth.  The Pacific Plate pushed beneath the Mariana Plate. This trench is located near Japan in the western Pacific Ocean.
The state of Alaska

The southern string of islands in Alaska. The convergent boundary between the Pacific and North American plate helped create these.

Other Great Resources:

Short Video on Convergent Boundaries:

Convergent Boundaries and Landforms:

Is it Dangerous to Live Near Convergent Boundaries?:

Convergent Boundaries, Earthquakes, and Tsunamis:

Written by: Varsha Rammohan.