Cirrostratus is a high cloud that commonly causes a halo-like effect around the sun. Altrostraus is a middle level cloud. It is uniform, thick, gray and frequently produces precipitation. Stratocumuli are low clouds that often form during the clearing period following a storm. Stratigraphy is the arrangement of rocks in layers or strata.
Scientists can find information about the past by studying rock strata.
Sediment from the sea may form a layer of rock. An erupting volcano may cover the sedimentary rock with a layer of lava. Pressure exerted on base layers by surface layers may change the characteristics of the base layers. An earthquake may cause folding of the layers. Rock strata can yield information about their origin and history.