In the foreground Cambrian age limestones are seen to dip to the east. Late Pleistocene glacial till overlying bedrock at East Point, Nahant. Great Ledge Block - a Ordovician age dolerite sill intruded into the Cambrian Weymouth Fm. Another view of Great Ledge Block A basalt dike has been eroded by waves to form a narrow ravine. Waves attack fractures and other weak spots to wear away the coast.
Students descend the rocks to examine a fault.
Students climbing back up after examining a fault. Before Lunch students examine the many rock types found in the beach gravel of Dive Beach. Rock types include local rocks such as limestone, mudstone, basalt, gabbro, and dolerite. Non-local pebbles include glacial erratics such as granite, rhyolite, gneiss, and schist. Human detritus such as rounded bricks, concrete, and metal are also part of the beach.