Plate Tectonics Play a Crucial Role in Sustaining Life on Earth

FROM THE LECTURE SERIES: A Field Guide to the Planets

By Sabine Stanley, Ph.D., Johns Hopkins University

The Earth’s outermost rigid shell is broken into a series of plates. These tectonic plates drift around—moving continents, causing earthquakes and volcanoes, and determining the composition of the air we breathe. The plates are a series of large blocks of rocks that make the Earth’s surface appear like a puzzle. Let’s solve this puzzle and see how it plays a major role in making our planet so vibrant and abundant.

Complete Earth view from space (Image: Volodymyr Nikulishyn/Shutterstock)

The pale blue dot photographed in 1990 by the Voyager 1 from 3.8 billion miles away is, in fact, the planet Earth. It shows that the Earth is just a speck of dust at the edge of the solar system. Similar pictures have been taken from the surface of Mars and from the Moon as well. But we know that the pale blue dot of planet Earth is special as it sustains life and habitability, although this may not be obvious from such distances.

Scientists believe that there are certain signs of life on Earth that can be observed from space. For instance, the Earth’s atmosphere has a distinct light spectrum, which indicates that oxygen and other gases are present on our planet. The light from Earth also changes with the seasons, meaning the spin axis of the Earth is tilted. Sensitive detectors could determine the length of a day on Earth as well as find the time between the Earth’s full rotations.

So, What Makes the Earth a Perfect Spot for Life?

Plate tectonics is one of the key characteristics of Earth that is believed to have played a major role in the evolution of complex life. The influence of plate tectonics on the Earth’s climate and carbon cycle, coupled with its role in generating a protective magnetosphere, helped various life-forms gain a foothold on the planet.

A diagram of the internal structure of the Earth showing the asthenosphere, mantle, and core.
The internal structure of Earth is layered in spherical shells: an outer silicate solid crust, a highly viscous asthenosphere and mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. (Image: Kelvinsong/CC BY-SA 3.0/Public domain)

Influence on Oceans and Climatic Conditions

Plate tectonics can change sea levels of local regions. Shallow waters that occur due to these changes in sea level can be ideal grounds for life to evolve on Earth. Scientists are of the opinion that there is a relationship between plate tectonics and major evolutionary events in the fossil record.

Another effect of tectonic plate movements is that the location of oceans keeps changing and so do ocean currents. A region’s climatic system is largely dependent on ocean currents, which in turn are influenced by the movement of continental plates. Ocean currents such as the Atlantic Meridional Overturning Circulation (AMOC) are the reason why places with the same latitudes in Europe and North America experience different temperatures. The AMOC carries warm water from the equatorial regions in the Atlantic northward. As the warm water releases heat into the atmosphere, places with similar latitudes in Europe experience much warmer weather compared to their counterparts in North America. 

Learn more about the Earth and how plate tectonics sets up life.

The Earth’s Carbon Cycle

As the tectonic plates keep moving, carbon is cycled and recycled within the various layers of the Earth. Plate tectonics plays a key role in the carbon cycle and in determining the amount of carbon dioxide in the atmosphere. The carbon dioxide in the atmosphere mixes with rain to form carbonic acid, which eventually weathers rocks. This process creates carbonates, such as limestone, which settle at the bottom of the oceans and subduct into the mantle. However, if all the carbon dioxide from the atmosphere were to enter the mantle, the Earth would freeze. The loss of this greenhouse gas is compensated for by the volcanic eruptions that occur at the subduction zone. These volcanoes release carbon dioxide into the atmosphere, thereby replenishing the same. Thus, the carbon cycle acts as the base for sustaining life on Earth.

This is a transcript from the video series A Field Guide to the Planets. Watch it now, on The Great Courses Plus.

Generating a Magnetic Field

A diagram showing the magnetosphere which safeguards Earth from solar winds.
The magnetic field created by internal motions of the core produces the magnetosphere which shields the surface of the Earth. (Image: NASA/Public domain)

The magnetosphere, or magnetic bubble, in space is generated by the Earth’s magnetic field. It protects our planet from the harmful effects of solar wind and ionizing particles from space. The magnetosphere deflects the continuous flow of plasma and charged particles released from the Sun and from space. It is important for the Earth’s core to cool rapidly to generate a magnetosphere. Plate tectonics opens the mantle coat regularly and releases heat, thereby swiftly cooling the Earth’s mantle. In effect, the Earth’s core cools rapidly, creating favorable circumstances for the creation of a magnetic field.

Learn more about the origin and evolution of Earth.

Role in Mountain Building

Buoyant continental rocks only partly subduct back into the Earth. These colliding continental blocks lead to the formation of mountains. The Himalayas are a classic example of how plate tectonics can influence both the geographical and biological landscape of the Earth. The collision of the Indian and Eurasian plates resulted in the formation of the Himalayas, the highest mountain range on the planet. The newly formed mountains, being more prone to weathering and erosion, erode important minerals to the ocean. These eroded minerals, such as phosphorus and calcium, act as building blocks for the emergence of life.

Common Questions About the Role of Plate Tectonics in Sustaining Life on Earth

Q: What are the sources of water on the Earth’s surface during early history?

Volcanic eruptions released gases such as carbon dioxide and water vapor to the Earth’s surface by a process called volcanic outgassing. This water vapor condensed to liquid form on the surface of the Earth. It is possible that a significant amount of water in the Earth’s early history came from volcanic outgassing.

Q: What is the role of carbon dioxide in sustaining life on Earth?

Carbon dioxide is an important greenhouse gas that helps trap heat in the atmosphere. This helps the Earth’s surface maintain the optimum temperature that would allow liquid water to be stable on its surface. Lack of carbon dioxide would result in a frozen planet.

Q: What is the Cambrian Explosion?

The Cambrian Explosion is the most important evolutionary event in the history of our planet. It is believed that when the phytoplanktons that thrived on the ocean floor released more oxygen, the Cambrian Explosion occurred. As a result, around 540 million years ago, life on Earth evolved from simple, single-celled organisms to innumerable complex multicellular animals. This evolution happened over a period of about 20 million years.

Q: What are latitudes?

A latitude is the imaginary line running horizontally through the globe. It is used to describe the position of a particular place on the surface of the Earth. It starts from zero degrees at the equator and ends at 90 degrees at the North and South Pole. To illustrate with an example, Denver, Colorado is at the same latitude as southern Italy.

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