Heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core. The convection currents move the plates. The movement of the plates, and the activity inside the Earth, is called plate tectonics . Plate tectonics cause earthquakes and volcanoes .

The mantle within the earth’s surface flows due to convection currents. These currents are mainly caused by a very hot material present in the deepest part of the mantle which rises upwards, then cools, sinks, again and again, repeating the same process of heating and rising.

Convection currents transfer heat from one place to another by mass motion of a fluid such as water, air or molten rock. The heat transfer function of convection currents drives the earth’s ocean currents, atmospheric weather and geology.

Convection Currents | A Level Geography. The plates that make up the Earth’s crust are continually moving at around 2-3cm per year.

Sixty percent of all active volcanoes occur at the boundaries between tectonic plates. Most volcanoes are found along a belt, called the “Ring of Fire” that encircles the Pacific Ocean. Some volcanoes, like those that form the Hawaiian Islands, occur in the interior of plates at areas called “hot spots.”

Volcanoes are most common in these geologically active boundaries. The two types of plate boundaries that are most likely to produce volcanic activity are divergent plate boundaries and convergent plate boundaries.

Plate tectonics is the large scale movement of Earth’s crust, and results in a number of distinct geologic settings. …

There are three kinds of plate tectonic boundaries: divergent, convergent, and transform plate boundaries. This image shows the three main types of plate boundaries: divergent, convergent, and transform. Image courtesy of the U.S. Geological Survey.

The relationships between plate tectonics and volcanism are shown on Figure 4.3. As summarized in Chapter 3, magma is formed at three main plate-tectonic settings: divergent boundaries (decompression melting), convergent boundaries (flux melting), and mantle plumes (decompression melting).

One example of a ridge is the Mid-Atlantic Ridge, an undersea chain of mountains that formed as two pairs of tectonic plates spread apart: the North American Plate and the Eurasian Plate in the north, and the South American Plate and the African Plate in the south.