Earth Science Scales
Official scales for earthquake magnitudes, mineral hardness, volcanic eruptions, space weather events, and cosmic impacts.
The Mohs Mineral Hardness Scale
The ten-mineral Mohs scale of relative hardness, based on what scratches what.
The ten-mineral Mohs scale of relative hardness, based on what scratches what.
Geologic Time Scale - Eons, Eras and Periods
The major divisions of geologic time.
The major divisions of geologic time.
Epochs of the Phanerozoic Eon
Epochs are the subdivisions of geologic periods; the Phanerozoic runs from 542 million years ago to today.
Epochs are the subdivisions of geologic periods; the Phanerozoic runs from 542 million years ago to today.
Measuring the Big One
From your About Geology Guide, an introduction to earthquake magnitude scales—Richter and the rest.
From your About Geology Guide, an introduction to earthquake magnitude scales—Richter and the rest.
Getting Intense with Earthquakes
From your About Geology Guide, an introduction to earthquake intensity scales.
From your About Geology Guide, an introduction to earthquake intensity scales.
Earthquake Intensity Scales Compared
Mercalli, Rossi-Forel, Omori, and European Macroseismic scales put side by side in one handy table.
Mercalli, Rossi-Forel, Omori, and European Macroseismic scales put side by side in one handy table.
Modified Mercalli Intensity Scale
How U.S. earthquakes are ranked from I to XII.
How U.S. earthquakes are ranked from I to XII.
European Macroseismic Scale
A summary of the most modern earthquake intensity scale, used in European countries.
A summary of the most modern earthquake intensity scale, used in European countries.
The Omori Earthquake Scale
The original seven-point Japanese seismic intensity standard, based on typical Japanese structures.
The original seven-point Japanese seismic intensity standard, based on typical Japanese structures.
Japanese Quake Intensity Scale of 1949
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 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.
Japanese Quake Intensity Scale of 1996
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.
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.
Space Weather Solar Radiation Storm Scale
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.
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.
Space Weather Geomagnetic Storm Scale
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.
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.
Space Weather Radio Blackout Scale
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.
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.
Torino Scale of Comet/Asteroid Collisions
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.
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.
2001 Tsunami Intensity Scale
This 12-point scale of tsunami intensity was proposed in 2001 by Gerassimos Papadopoulos and Fumihiko Imamura.
This 12-point scale of tsunami intensity was proposed in 2001 by Gerassimos Papadopoulos and Fumihiko Imamura.
Tsunami Intensity Scale (Sieberg-Ambraseys)
This early six-point tsunami intensity scale was modeled after the scales used for earthquakes.
This early six-point tsunami intensity scale was modeled after the scales used for earthquakes.
Volcanic Explosivity Index
The VEI classifies the severity of volcanic eruptions from 0 to 8 based on a mixture of evidence.
The VEI classifies the severity of volcanic eruptions from 0 to 8 based on a mixture of evidence.