Earth Science Scales

The 10-mineral Mohs scale of relative hardness is 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.

The modified Mercalli intensity scale rates the impact of quakes from I to XII.

The best intensity scale for scientific and planning purposes, used throughout Europe.

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 and Palermo scales both apply to possible collisions with asteroids and comets.

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 2001 Papadopoulos-Imamura intensity scale rates the impact of tsunamis from I to XII.

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.