Outer core

The outer core is the liquid layer of Earth's core that lies between the mantle and inner core. The outer core makes up about 30 percent of Earth's mass. It begins at a depth of 1,800 miles from Earth's surface and is approximately 1,430 miles thick. It consists mainly of liquid iron and nickel. This layer is very hot and measures between 7,200 and 9,000 degrees Fahrenheit. The boundary between the inner and outer core reaches temperatures of more than 10,000 degrees Fahrenheit. Scientists believe the outer core also contains small amounts of elements such as oxygen and sulfur.

Earth's core is always moving. Scientists consider this phenomenon responsible for Earth's magnetic field. When the outer core's liquid metals shift and rotate, the movement can change the location of the magnetic North and South poles.

Formation of Earth's Core

Earth's core took billions of years to form. It began with the formation of the solar system, which originated from the Big Bang approximately thirteen billion years ago. A cloud of interstellar matter rotated throughout space until another explosion caused the materials to tighten and form into a flat, disc-like shape. This disc rotated at an even faster pace. The Sun eventually formed at the center of this system, and the remaining materials began to form protoplanets, including an early Earth.

As Earth continued to grow, its interior began to organize and separate into different layers. The core did not take on a more distinct form until Earth was about thirty million years old. After its initial creation, the core took tens of thousands of years to form completely. As Earth's temperature rose, the materials making up the inner layers began to melt. Gravity caused these materials to sink into Earth's center, forming the core. The core then separated into an inner and outer layer. Mostly solid iron composes the inner core. Though this iron is very hot, it does not melt because of the planet's pressure. The outer core is made of mostly iron and nickel, which combine to form an alloy. This alloy melts as heat from the inner core transfers outward, making the outer core a liquid layer.

Investigation of Earth's Core

The intense heat of Earth's core prevents scientists from being able to study it directly, but drilling Earth's surface and studying earthquakes has helped humans understand some of the core's properties. Researchers received their first idea of the core's true temperature in the 1960s by drilling deep into Earth's surface. The temperature was much hotter than they had originally thought, which presented several problems when drilling. The science of seismology, the study of the propagation of waves through Earth, also helped scientists to understand the interior structure of the planet. The study of earthquakes led to the discovery of the composition of the inner and outer core.

Danish seismologist Inge Lehmann was the first to decipher Earth's interior. She studied the seismic wave activity of earthquakes and determined that certain waves could travel through both solids and liquids, while others could travel only through solids. Based on research she conducted after a large earthquake in New Zealand in 1929, Lehmann concluded that the types of seismic waves produced during the quake could only have happened if Earth's core was solid and liquid. Therefore, she proposed the existence of a solid inner core and a liquid outer core. The study of seismology continued to shed light on Earth's core. In 2010, scientists used seismological research to determine that more than just iron and nickel composed the outer core. The measurements of seismic wave speed suggested that the uppermost area of the outer core also contained about 10 percent of lighter elements such as oxygen and sulfur. The progressive improvement of seismological instruments has made core research more accurate.

Technology cannot give scientists explicit access to Earth's core. They must gather some information through deductive reasoning. Scientists decided the core must be very dense since the average density of Earth's surface materials and the overall density of Earth leaves a gap in mass and volume. Geophysicists that study meteorites also make inferences based on their belief that Earth's structure is similar to a chondrite meteorite. These meteorites were once a part of asteroids that were too small to grow into layered planets; therefore, researchers believe they are composed of materials similar to Earth's interior.

Outer Core's Effect on Earth's Magnetic Field

Scientists believe Earth's outer core is primarily responsible for maintaining Earth's magnetic field based on a phenomenon detailed in the dynamo theory. According to this theory, magnetic fields can be created and sustained by a fluid with three properties: rotation, convection (circular movement of liquid due to temperature change), and electricity-conducting capabilities. The outer core has all these qualities. Scientists believe the magnetic field within Earth's outer core is around fifty times stronger than the magnetic field of Earth's surface. They also believe the intense heat of the inner core helps the outer core balance out the magnetic field.

Bibliography

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Choi, Charles Q. "Earth's Core Has Another Layer, Scientists Claim." Live Science, 8 Dec. 2010, www.livescience.com/10324-earth-core-layer-scientists-claim.html. Accessed 24 Nov. 2024.

"Core." National Geographic, 11 June 2024, education.nationalgeographic.org/resource/core/. Accessed 24 Nov. 2024.

Howell, Elizabeth. "Earth's Core 1,000 Degrees Hotter Than Expected." Live Science, 25 Apr. 2013, www.livescience.com/29054-earth-core-hotter.html. Accessed 24 Nov. 2024.

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