Earth is a dynamic planet, experiencing constant changes in its surface and internal structure. In fact, some scientists believe that the earth is currently undergoing a period of accelerated change. One of the most significant factors in these changes has been plate tectonics. Plate tectonics is the theory that the outermost, rigid layer of the earth known as the crust is divided into several large plates. These plates float on a semi-fluid mantle and move at varying rates.
These movements cause earthquakes and volcanoes and sometimes create new ocean floors and islands, such as Hawaii. As a result, plate tectonics has significantly shaped our planet’s surface over millions of years. Geologists have identified three ways plate tectonics have impacted the earth: creating mountains, causing earthquakes and volcanoes, and influencing oceanic circulation patterns.
The first major impact of plate tectonics is on mountain formation. The strong, overlapping currents of the convective mantle cause vertical movement between the plates. This movement creates pressure underneath the plates, which creates magma. Magma is pushed to the surface through faults or volcanoes, which hardens into rock.
Over time this process builds up mountains. The mountain formation process can be slow or quick, depending on how quickly tectonic plates overlap and volcanoes erupt. This makes it difficult to predict when or where a mountain will form, but it is estimated that hundreds of mountains will eventually reach 20,000 feet high over time.
A more direct role that plate tectonics plays in mountain formation is through subduction zones. Subduction zones are areas where oceanic plates converge with other plates, which creates a chain of volcanoes. As the plates collide, the underplate is forced down into the mantle at a rate of two to four inches per year, which creates tremendous amounts of heat and pressure.
This causes the volcanic rock to melt and form magma. This process is known as subduction. In some cases, these processes create volcanoes that can be active for millions of years. Over time this process also builds up mountains, but unlike magma buildup from many volcanoes, it is a relatively slow process that has taken place over millions of years.
Another major impact that plate tectonics has on our planet is earthquakes and volcanoes. Scientists have classified plate tectonics into three main types. The three are divergent, convergent, and transform.
Divergent plate boundaries are the areas where the plates are moving apart. These volcanoes form in regions where two plates are moving apart at very different rates or where two plates meet at a glacier or mountain range. Divergent boundaries occur in zones where one plate moves away from another at an angle of 45 degrees or more to the direction of displacement while allowing other plates to remain stationary.
Convergent plate boundaries occur when two plates converge under the force of gravity. Convergent boundaries occur when one plate is diving faster than other parts but still slower than continental drift. Most of the earthquakes that occur happen under areas of convergent boundaries.
Transform plate boundaries occur when one plate slides horizontally past another plate, mostly along the mid-ocean ridge system. Transform boundaries have a high rate of earthquake activity but not as many volcanoes. Instead, they form a rift that creates a fracture in the earth’s crust.
Over time these fractures slowly spread and caused continents to break apart. In some cases, transform boundaries can be extremely destructive. For example, the Indian Ocean earthquake of December 26, 2004, created a tsunami with waves up to 100 feet tall that killed almost 300,000 people and displaced 3 million more from the coastal regions in the Indian Ocean basin and surrounding countries.
The final way that plate tectonics impacts the earth is through ocean currents. The movement of tectonic plates creates a current in the mantle beneath them. The current is forced through cracks and divides, which creates a series of five ocean basins.
The Pacific Ocean has three plates that move around it, creating two large walls surrounding it, where many islands have been formed from volcanic activity. In the Atlantic Ocean, two major plates move around it, creating a rift in the middle of the ocean where most of the world’s deep-sea trenches are located.
In fact, three-fourths of all earthquakes take place in just these three areas alone. Despite the destructive power of these plates, they also carry nutrients and oxygen to the deep-sea trenches, which are one of the few places on earth where life can exist without the presence of sunlight.
Plate tectonics has had a significant impact on every continent, every ocean, and every continent. Scientists continue to study how these changes impact our planet and what effect they may have in the future. As discoveries are made about plate tectonics, it is becoming increasingly clear that plate tectonics processes play an important role in shaping our planet.