California's San Andreas Fault marks the boundary between the Pacific and North American Plates.
If you think objects that move only a few centimeters each year cannot profoundly influence life on Earth, think again. Lithospheric plates move at about the same rate your fingernails grow, yet they created the world's tallest mountains and deepest oceanic trenches. Imperceptible plate movement over millions of years has shaped Earth's surface and caused some of the planet's most awe-inspiring, and sometimes terrifying, natural events.
Plate Tectonics Theory
The theory of plate tectonics developed from the original concept of continental drift, an idea that was widely dismissed by the scientific community in the early 20th century. By the 1960s, plate tectonics was universally accepted as the primary force behind earthquakes, volcanism, continental drift, and the creation of mountain ranges and rift zones.
Earth's surface, or crust, combines with the uppermost part of the solid mantle to form a rigid shell about 50 miles thick called the lithosphere that is broken into several pieces called lithospheric, or tectonic, plates. These plates, which fit together like a spherical jigsaw puzzle, float on a semi-fluid layer of the mantle called the athenosphere. Tectonic plates are in constant motion relative to one another, colliding, separating and slipping sideways in a slow-motion process with far-reaching effects on nearly all life on Earth.
Plate Tectonics and Earthquakes
Earthquakes occur primarily along the boundaries of tectonic plates, and are among the most violent, destructive and frightening of Earth's natural phenomena. They are caused by an abrupt release of accumulated stress and tension created by plates converging, subducting or sliding sideways past one another. The history of devastation and death resulting from earthquakes and their after-effects, such as tsunamis, is well-documented. A catastrophic 2004 quake in the Indian Ocean created massive tsunamis that killed more than 230,000 people in 14 countries. The 2011 Tohuku earthquake and tsunami obliterated the Japanese coastal city of Sendai resulting in over 15,000 deaths. The Tohuku event also affected the worldwide economy and severely damaged the Fukushima nuclear power plant, contaminating land for miles around and sending clouds of radioactive particles into the atmosphere.
Plate Tectonics and Volcanism
Like earthquakes, volcanism typically occurs near plate boundaries. Converging plates create subduction zones where an oceanic plate subducts, or dives under a continental plate or another oceanic plate. The descending plate is pushed ever deeper, creating an oceanic trench, destroying the crust material and turning it to magma through friction, heat and pressure. The lighter magma then rises through more dense surrounding rock, eventually reaching the surface to form volcanoes. The Pacific Ocean "Ring of Fire" was created through the subduction process.
The Effects of Volcanism
The effects of volcanism are wide-ranging. Active volcanoes are a threat to nearby plant and animal life. Major volcanic eruptions throughout history have altered landscapes, destroyed forest and farmland, and resulted in significant loss of life and property. When the Colombian volcano Nevada del Ruiz erupted in 1985, it melted glaciers and and buried the town of Armero, 30 miles away under a layer of mud and debris, resulting in more than 20,000 deaths. The colossal eruption of Mt. Tambora in Indonesia had a global effect. In the largest eruption ever recorded, Tambora ejected an ash cloud that temporarily changed Earth's climate, blocking sunlight and reducing temperatures, causing the greatest famine of the 19th century, as crops failed and livestock died throughout much of the Northern Hemisphere. The positive effects of volcanoes include the creation of nutrient-rich, fertile soil that produces crops ranging from coffee and tea to a variety of tropical fruits.
Biodiversity
Tectonic plate movement contributes to the biodiversity of Earth. As extinct oceanic volcanoes slowly erode into the sea, their caldera become habitats supporting a wide variety of marine life. Lava from Kilauea makes the island of Hawaii a little bigger each year, creating new marine oceanic environments. Strange organisms adapt to life in the perpetual darkness, crushing pressures and near freezing temperatures of deep-sea trenches, while others adapt to life near diverging plate boundaries that create hydrothermal vents on the ocean floor, called black smokers, where water temperatures may exceed 400 degrees Fahrenheit.
Tags: Plate Tectonics, adapt life, continental drift, each year, Earth surface, earthquakes volcanism, life Earth
