The Paleozoic is the second era of geologic time that lasted from 570 million till about 225 million years before the present. If the deposits are buried, the heat and pressure may turn the peat into coal. Periwinkles are abundant in this part of the rocky intertidal shore but since they are mobile, this zone is often indistinct. For this reason, some biologists don't include this as one of the life zones on the rocky shore. Plankton are often microscopic and are an important food source for other aquatic community.
Most marine worms are polychaetes.
A quadrat is a square frame of any size that can be placed randomly or along a transect line. The organisms within the square are counted or measured. This life zone is submerged at every high tide and is dominated by brown seaweed, such as knotted wrack and rockweed. For this reason this zone is often called the brown zone. Sedimentary rocks form when sediments accumulate and are then consolidated.