An earth tremor is another term for an earthquake, although it is most commonly used to describe earthquakes of low intensity. Earthquakes are measured with tools called seismographs, and their intensity is rated on a logarithmic scale, called the Richter scale. The Richter scale is not useful for earthquakes that rank higher than a level 8 earthquake.Know More
Earthquakes occur when the earth’s tectonic plates move and contact other plates. Sometimes the plates rub against each other laterally, while other times one plate moves underneath another. When this happens, it is called a subduction zone or a subduction-caused earthquake. In some particularly violent earthquakes, two plates collide into each other. This type of collision may even cause mountains to form, which happened millions of years ago when the Indian subcontinent crashed into Asia, producing the Himalayas.
Earthquakes are rather common, though few are strong enough to cause much damage. People may not even feel very weak earthquakes. The center of the disturbance is called the earthquake’s epicenter, and epicenters usually occur along major fault lines, where two plates contact each other. Many large and active fault lines occur around the margin of the Pacific Ocean, which has given the region the name “ring of fire” for all of the earthquakes and volcanoes in the region.Learn More
The Earth has a radius of 3,959 miles, a diameter of 7,926 miles and a circumference of 24,902 miles. Earth has a mass of 6.6 sextillion tons and a total surface area of 197 million square miles. It is the fifth largest planet in the solar system.Full Answer >
Astronomers theorize that over 4.5 billion years ago, Theia, an object about the size of Mars, collided with Earth to create a tilted axis. This is called "the giant impact theory." Prior to this event, the axis was straight at 180 degrees.Full Answer >
The term "eustatic" refers to the global sea level. This is opposed to the isostatic sea level, which is a local measurement that is often a result of tides. Eustatic sea level changes are global, and they are often the result of major upheavals to the climate or ocean basin.Full Answer >
The Earth's equatorial circumference is 24,902 miles. Due mainly to the oblate shape of the Earth, its circumference along a line of longitude comes out to be somewhat less: 24,860 miles. Earth has a surface area of 197 million square miles.Full Answer >