The Geologic Time Scale is divided into huge blocks of time called eras. Eras are defined by major changes in the fossils found in the rock layers that were formed during those time spans.

Altocumulus, altostratus, cirrocumuls, cirrostratus, cirrus, cumulonimbus, cumulus, nimbostratus, stratocumulus, stratus 8.) clouds with tallest vertical development 9.) low altitude clouds in solid layers that produce rain 10.) high altitude thin flat layers of clouds 11.) rain clouds that form under stable atmospheric conditions 12.) middle altitude clouds with globular appearance