Tectonic plates are the large slabs of solid rock that form the Earth’s crust and upper mantle. These plates float on the superheated mantle beneath them and the continents and oceans rest on these plates. The tectonic plates are in constant motion due to the heat of the mantle, but they move around very slowly at a rate of 5-10 cm per year. On average the pates are about 100km (61mi) thick, but the overall size of the plates varies greatly. Let’s take a look at the number of tectonic plates on Earth.
How many tectonic plates are there on Earth?
There are seven primary tectonic plates that make up most of the seven continents and the pacific ocean. These are the African Plate, Antarctic Plate, Eurasian Plate, Indo-Australian Plate, North American Plate, Pacific Plate and South American Plate. There are also 8 secondary tectonic plates that are smaller than the primary plates. These are the Arabian Plate, Caribbean Plate, Cocos Plate, Indian Plate, Juan de Fuca Plate, Nazca Plate, Philippine Sea Plate and the Scotia Plate. Together these make up the 15 major tectonic plates of the Earth.
There are also a number of tertiary plates that are mostly microplates within the major tectonic plates. The list is constantly changing because experts do not always agree and new research is always being conducted. As of November 2011 there are 59 tertiary tectonic plates.
Did you know?
Both earthquakes and volcanic activity occur most frequently along the boundaries of these plates.