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.
The southern oscillation is the seesaw pattern of atmospheric pressure change that occurs between the eastern and western Pacific Ocean. These pressure changes alter the directions in which the trade winds blow. The interaction of these events can cause extreme weather events in many parts of the world. Till Till is an unsorted mix of clay, sand, boulders, gravel and other debris deposited by a glacier as it melts. Tree rings Examination of a cross section of a trunk reveals concentric pattern in the wood called tree rings.