Earth is a terrestrial planet, meaning that it is a rocky body, rather than a gas giant like Jupiter. It is the largest of the four terrestrial planets in size and mass. Of these four planets, Earth also has the highest density, the highest surface gravity, the strongest magnetic field, and fastest rotation,[65] and is probably the only one with active plate tectonics.[66]
Shape
Main article: Figure of the Earth
Chimborazo, Ecuador. The furthermost point on the Earth's surface from its center.[67]
The shape of the Earth approximates an oblate spheroid, a sphere flattened along the axis from pole to pole such that there is a bulge around the equator.[68] This bulge results from the rotation of the Earth, and causes the diameter at the equator to be 43 km (kilometer) larger than the pole-to-pole diameter.[69] For this reason the furthest point on the surface from the Earth's center of mass is the Chimborazo volcano in Ecuador.[70] The average diameter of the reference spheroid is about 12,742 km, which is approximately 40,000 km/p, as the meter was originally defined as 1/10,000,000 of the distance from the equator to the North Pole through Paris, France.[71]
Local topography deviates from this idealized spheroid, although on a global scale, these deviations are small: Earth has a tolerance of about one part in about 584, or 0.17%, from the reference spheroid, which is less than the 0.22% tolerance allowed in billiard balls.[72] The largest local deviations in the rocky surface of the Earth are Mount Everest (8,848 m above local sea level) and the Mariana Trench (10,911 m below local sea level). Due to the equatorial bulge, the surface locations farthest from the center of the Earth are the summits of Mount Chimborazo in Ecuador and Huascarán in Peru.
Shape
Main article: Figure of the Earth
Chimborazo, Ecuador. The furthermost point on the Earth's surface from its center.[67]
The shape of the Earth approximates an oblate spheroid, a sphere flattened along the axis from pole to pole such that there is a bulge around the equator.[68] This bulge results from the rotation of the Earth, and causes the diameter at the equator to be 43 km (kilometer) larger than the pole-to-pole diameter.[69] For this reason the furthest point on the surface from the Earth's center of mass is the Chimborazo volcano in Ecuador.[70] The average diameter of the reference spheroid is about 12,742 km, which is approximately 40,000 km/p, as the meter was originally defined as 1/10,000,000 of the distance from the equator to the North Pole through Paris, France.[71]
Local topography deviates from this idealized spheroid, although on a global scale, these deviations are small: Earth has a tolerance of about one part in about 584, or 0.17%, from the reference spheroid, which is less than the 0.22% tolerance allowed in billiard balls.[72] The largest local deviations in the rocky surface of the Earth are Mount Everest (8,848 m above local sea level) and the Mariana Trench (10,911 m below local sea level). Due to the equatorial bulge, the surface locations farthest from the center of the Earth are the summits of Mount Chimborazo in Ecuador and Huascarán in Peru.
