Map of Tectonic Plates and Their Boundaries

Map of tectonic plates
From This Dynamic Planet..

This map, published in 2006 by the U.S. Geological Survey, gives much more detail than the basic plate map. It shows 21 of the major plates, as well as their movements and boundaries. Convergent (colliding) boundaries are shown as a black line with teeth, divergent (spreading) boundaries as solid red lines, and transform (sliding alongside) boundaries as solid black lines.

Diffuse boundaries, which are broad zones of deformation, are highlighted in pink. They are generally areas of orogeny or mountain building.  

The teeth along the convergent boundaries mark the upper side, which is overriding the other side. The convergent boundaries correspond to subduction zones where an oceanic plate is involved. Where two continental plates collide, neither is dense enough to subduct below the other. Instead, the crust thickens and forms large mountain chains and plateaus.

An example of this is the ongoing collision of the continental Indian plate and continental Eurasian plate. The landmasses began colliding around 50 million years ago, thickening the crust to great extents. The result of this process, the Tibetan Plateau, is perhaps the largest and highest landform to have ever existed on Earth. 

Continental divergent plates exist in East Africa and Iceland, but most of the divergent boundaries are between oceanic plates. As the plates split apart, whether, on land or the ocean floor, magma rises to fill in the empty space. It cools and latches onto the spreading plates, creating new Earth. This process forms rift valleys on land and mid-ocean ridges along the seafloor. One of the most dramatic effects of divergent boundaries on land can be seen in the Danakil Depression, in the Afar Triangle region of East Africa.

You may notice that the divergent boundaries are periodically broken up by black transform boundaries, forming a zig-zag or staircase formation. This is due to the unequal speeds at which the plates diverge; when a section of mid-ocean ridge moves faster or slower alongside another, a transform fault forms between them. These transform zones are sometimes called "conservative boundaries," because they neither create (as for divergent boundaries) nor destroy land (as convergent boundaries).

The map also lists the Earth's major hotspots. Most volcanic activity on Earth occurs at divergent or convergent boundaries, with hotspots being the exception. It is generally accepted that hotspots form as the crust moves over a long-lasting, anomalously hot area of the mantle. The exact mechanisms behind their existence are not fully understood, but geologists recognize that over 100 hotspots have been active in the past 10 million years.

They can be located near plate boundaries, like in Iceland (which sits on top of a divergent boundary and hotspot), but are often found thousands of miles away. The Hawaii hotspot, for example, is almost 2,000 miles away from the nearest boundary. 

Seven of the world's major tectonic plates (Pacific, Africa, Antarctica, North America, Eurasia, Australia, and South America) make up around 84 percent of the Earth's total surface. This map shows those and also includes many other plates that are too small to label.

Geologists refer to the very small ones as "microplates," although that term has loose definitions. The Juan de Fuca plate, for example, is very small (ranked 22nd in size) and could be considered a microplate. Its role in the discovery of seafloor spreading, however, leads to its inclusion in almost every tectonic map.

Despite their small size, these microplates can still pack a big tectonic punch. The 7.0 magnitude 2010 Haiti earthquake, for instance, occurred along the edge of the Gonâve microplate and claimed hundreds of thousands of lives. 

Today, there are more than 50 recognized plates, microplates, and blocks.