The geology of Rhode Island is based on nearly one billion year old igneous crystalline basement rocks formed as part of the microcontinent Avalonia that collided with the supercontinent Gondwana. The region experienced substantial folding associated with its landlocked position during the Alleghanian orogeny mountain building event. The region accumulated sedimentary rocks, including small deposits of coal. The region was covered with thick Atlantic Coastal Plain sediments, with the erosion of the Appalachians and the creation of the Atlantic Ocean throughout the past 200 million years. These surficial sediments and soils were substantially reworked by the Pleistocene glaciations. The state's geology is part of the broader geology of New England.
