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At convergent plate boundaries where an oceanic plate meets a continental plate, oceanic crust is forced down into the Earth’s mantle and begins to melt. The melted rock rises into and through the overlying plate as magma, often forming a chain of volcanoes parallel to the plate boundary.
If two tectonic plates collide, they form a convergent plate boundary. Usually, one of the converging plates will move beneath the other, a process known as subduction. Deep trenches are features often formed where tectonic plates are being subducted and earthquakes are common at subduction zones as well.
Between the Mariana Trench and the island volcanoes, huge mud volcanoes provide a window into the boundary between two tectonic plates that have been colliding for over 50 million years and harbor unique communities of organisms that thrive in the most extreme fluid composition recorded in the oceans.
Mid-ocean ridges occur along divergent plate boundaries, where new ocean floor is created as the Earth’s tectonic plates spread apart. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt.
The Ring of Fire is the result of plate tectonics. Much of the volcanic activity occurs along subduction zones, which are convergent plate boundaries where two tectonic plates come together. The heavier plate is shoved (or subducted) under the other plate.
Deep earthquakes can happen only where there is solid rock hundreds of kilometers below the surface. That only occurs at convergent boundaries, where plates are sometimes pushed deep beneath the surface and into the mantle.
The topography of the seafloor indicates the presence of a convergent plate boundary. Where is the boundary?
Most divergent plate boundaries are underwater (Iceland is an exception), and form submarine mountain ranges called oceanic spreading ridges. While the process is volcanic, volcanoes and earthquakes along oceanic spreading ridges are not as violent as they are at convergent plate boundaries.
The Northeast Caribbean – Plate Tectonics in Action. by Jason D. Chaytor, Research Geologist, U.S. Geological Survey. Figure 1: Map of the North American – Caribbean tectonic plate boundary. Colors denote depth below sea level and elevation on land.
At these boundaries, magma (molten rock) rises from deep within the Earth and erupts to form new crust on the litho- sphere. Most divergent plate boundaries are under- water (Iceland is an exception), and form subma- rine mountain ranges called “oceanic spreading centers” or “mid-ocean ridges.”.