Official scales for earthquake magnitudes, mineral hardness, volcanic eruptions, space weather events, and cosmic impacts.
The ten-mineral Mohs scale of relative hardness, based on what scratches what.
The major divisions of geologic time.
Epochs are the subdivisions of geologic periods; the Phanerozoic runs from 542 million years ago to today.
From your About Geology Guide, an introduction to earthquake magnitude scales—Richter and the rest.
From your About Geology Guide, an introduction to earthquake intensity scales.
Mercalli, Rossi-Forel, Omori, and European Macroseismic scales put side by side in one handy table.
How U.S. earthquakes are ranked from I to XII.
A summary of the most modern earthquake intensity scale, used in European countries.
The original seven-point Japanese seismic intensity standard, based on typical Japanese structures.
The Japanese Meteorological Agency (JMA) 1949 Seismic Intensity Scale was the successor to the Omori scale, used until 1996. This page is from the Japanese government.
The modern version of the Japanese scale is based on instrumentally recorded accelerations and changes the traditional seven categories to ten. This page is from the Japanese Meteorological Agency.
Bursts of hard radiation from the sun affect high-altitude workers like airline pilots and astronauts. They also can kill or disable satellites and affect radio communications at high latitudes.
When solar wind bursts push the Earth's magnetosphere around, the geomagnetic havoc can shake up electric power grids, damage spacecraft, send dangerous electric surges down pipelines, and wipe out radio navigation signals.
X-ray outbursts from the sun can blank out radio communications over the entire daylight side of the Earth. Here's the different levels of disruption due to this aspect of space weather.
The Torino Scale measures the magnitude of the threat to life on Earth from asteroid and cometary impacts. If we're lucky, it won't be used in our lifetimes.
This 12-point scale of tsunami intensity was proposed in 2001 by Gerassimos Papadopoulos and Fumihiko Imamura.
This early six-point tsunami intensity scale was modeled after the scales used for earthquakes.
The VEI classifies the severity of volcanic eruptions from 0 to 8 based on a mixture of evidence.
