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Earth Science Scales
Official scales for earthquake magnitudes, mineral hardness, volcanic eruptions, space weather events, and cosmic impacts.
The Mohs Mineral Hardness Scale
The 10-mineral Mohs scale of relative hardness is based on what scratches what.
Geologic Time Scale - Eons, Eras and Periods
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.
Measuring the Big One
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.
Earthquake Intensity Scales Compared
Mercalli, Rossi-Forel, Omori, and European Macroseismic scales put side by side in one handy table.
Mercalli Earthquake Intensity Scale
The modified Mercalli intensity scale rates the impact of quakes from I to XII.
European Macroseismic Scale (EMS98)
The best intensity scale for scientific and planning purposes, used throughout Europe.
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.
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.
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.
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.
Cosmic Impact Scales
The Torino and Palermo scales both apply to possible collisions with asteroids and comets.
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.
Tsunami Intensity Scale of 2001
The 2001 Papadopoulos-Imamura intensity scale rates the impact of tsunamis from I to XII.
Tsunami Intensity Scale (Sieberg-Ambraseys)
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.
