Earth is the third planet from the Sun. Be a home for all living things. There are so many characteristics of the earth that support the survival of living things. According to NASA, the earth and moon formed about 4.5 billion years ago. The earth's surface is known for its continents. The largest continent is known as Afro-Eurasia or is broken up into Africa, Europe and Asia. It has a total area of 32,800,000 square miles. This continent emerged due to the process of the earth's crust moving in geological time periods. Some geologists have also found several continents buried under the earth's surface due to shifts in the crust. When viewed from space photos, the earth looks round. However, the actual shape is an ellipsoid and also changes shape frequently. According to the Ocean Service, the ellipsoid shape of the Earth is not enough to describe the unique and ever-changing Earth. Planet Earth is fatter at the equator than at the poles by about 70,000 feet. This is due to the centrifugal force created by the constant rotation of the earth. The mountains towering over the earth at nearly 30,000 feet and ocean trenches more than 36,000 feet deep (compared to sea level) further distort the shape of the Earth. In addition, the shape of the sea surface on earth is also irregular. A slight variation in the Earth's gravitational field can cause permanent hills and valleys at sea level to exceed 300 feet relative to the ellipsoid. In addition, the shape of the earth is always changing. Sometimes these changes occur periodically, as is the case with the daily tides that affect the oceans and the earth's crust.
Sometimes Earth's changes are slow, such as shifting tectonic plates or rebounding the crust after a thick layer of ice melts. Sometimes the shape of the earth also changes in violent episodic ways, especially during earthquakes, volcanic eruptions, or meteor strikes. The National Geodetic Survey measures and monitors planet earth constantly changing. Geodesy is the science of measuring and monitoring the size and shape of the earth, including its gravitational field, and determining the location of points on the earth's surface.
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