Although the Richter Scale is mentioned most often in the media when a quake
occurs, there is a more precise scale in use today that is based on the mathematics of
motions caused by the earthquake. Called moment magnitude,this method uses a
physical quantity related to the total energy released in the quake, which is called a
moment. Seismologists can also deduce moment magnitude from a fault’s geometry
in the field or a seismogram reading. Scientists occasionally use moment magnitude
when describing an earthquake event to the public, but because the concept is so diffi-
cult to explain the number is often translated into the Richter Scale.What is sea level?
Sea levelis the height of the ocean’s surface at a certain spot and depends on changing
conditions. It is also the basis for most Earth surface measurements, because sea lev-
els are used as a reference point in determining land elevations and ocean depths.
Scientists have averaged out the highest and lowest altitudes and depths from sea
level locations: The highest is Mount Everest (Nepal-Tibet), which measures 29,022
feet, 7 inches (8,846 meters) above sea level; the lowest on land is the Dead Sea (Israel-
Jordan), which measures 1,299 feet (396 meters) below sea level. The greatest depth
below sea level is the Mariana Trench in the Pacific Ocean, a deep chasm measuring
302 36,201 feet (11,033 meters) below sea level.
Mt. Everest (right peak, with Mt. Nuptse at left) in Nepal, rising to a height of 29,022 feet, is the tallest mountain
on Earth when measuring height compared to sea level. National Geographic/Getty Images.