The Earth's core is a complex structure that is composed of two parts that are both liquid and solid. The reason for this structure is to provide a magnetic field for the Earth; however, this changes from time to time.
Background of the Earth's Composition
The Earth is a very complex world and the interior is no exception. In order, the Earth is composed of the crust, the upper and lower mantle, and lastly the outer and inner core. The further down the interior, the greater the density of the materials that compose each of these levels. In this respect, the outer and inner core are some of the most dense regions located in the Earth.
The core is very dynamic and is composed of the outer core which is about 1403 miles (2259 kilometers) thick and the inner core which about 759 miles (1221 kilometers) thick. The outer core is composed mostly of liquid and consists of a mixture of iron, oxygen, sulfur, and nickel. Some of these are composed of alloys such as an iron-nickel mixture. The inner core is different in that it is entirely composed of solid iron. Due to the high pressure, solid iron is formed.
Magnetism and the Earth's Health
The core as a whole is responsible for creating magnetic fields that surround the Earth. The core creates magnetism through the process of the dynamo effect. Essentially, the core's movement and the outer core's liquid iron creates magnetism. This process creates an electrical current and process of convention that form the magnetic field that surrounds the earth.
The magnetic field is important in that it protects the Earth from high charged particles that are formed solar storms and solar radiation. If this field decreases, electrical and technical equipment that are present in modern technology, such as computers and airplanes, are at risk for failure. According to Kimberly Johnson, changes in the Earth's core are allowing the magnetic field to decrease in power in certain areas of the world such as the South Atlantic. Even though this view is mixed among scientists, the majority agree that the magnetic field is important for the Earth's health.
It is thought that these changes have an effect on the magnetic field in the Earth. One of the most common examples includes the movement of the north magnetic pole. This pole has been recorded as moving ever since its first discovery in 1831 by James Ross. Over time, this pole has constantly moved north and is currently located in the Arctic Circle.
The Earth's core also occasionally allows the north and south magnetic poles to switch. Scientists believe that this phenomenon occurs roughly every 300,000 years and currently the last one happened 780,000 years ago. This process does not happen instantly, rather it can take thousands of years for this phenomenon to happen.
So why do these magnetic poles move? According to Lamont-Doherty Earth Observatory scientists, it is thought that the Earth's core spins faster than the Earth itself and in the process produces a magnetic field. They believe that the core moves two-thirds faster than the Earth itself. Since the inner core is moving ahead of the Earth, its location influences where the magnetic poles are located. Even though it appears the magnetic poles move, they depend on the movement of the inner core.
- Datillo. "Composition and Internal Structure of the Earth." http://faculty.weber.edu/bdattilo/shknbk/notes/cmpstrct.htm
- Johnson, Kimberly. "Earth's Core, Magnetic Field Changing Fast, Study Says." http://news.nationalgeographic.com/news/2008/06/080630-earth-core.html
- NASA. "Earth's Inconstant Magnetic Field." http://science.nasa.gov/science-news/science-at-nasa/2003/29dec_magneticfield/
- Robertson, Eugene C. "The Interior of the Earth." http://pubs.usgs.gov/gip/interior/
- Song, Xiaodong, Paul G. Richards. "Core Spins Faster Than Earth, Lamont Scientists Find." http://www.columbia.edu/cu/record/archives/vol22/vol22_iss1/Core_Spin.html
- NASA. "Magnetic Field Earth." http://commons.wikimedia.org/wiki/File:Magnetic_Field_Earth.png
- United States Federal Government. "Magnetic Poles Movement." http://commons.wikimedia.org/wiki/File:Magnetic_Poles_Movement.gif
- United States Federal Government."NASA Main World." http://commons.wikimedia.org/wiki/File:NASA_54558main_world_med1.gif