What is the secong layer of the earth?

Explain the reason for having an equator and a prime meridian. how do these two lines us to navigate our world? describe your opinion in at least two to three sentences.

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

Arow of elements on the periodic table is called an