When hundreds or thousands of coral polyps build their skeletons close together, they create a calcium carbonate structure that provides habitat and food for a variety of organisms. This is known as a coral reef. Explore a virtual coral reef. More Info - Common Coral Forms; More Info - Fringing Reefs
Arch Cape is an unincorporated community in Clatsop County, Oregon, United States. It is located along the Pacific coast about 4 miles south of Cannon Beach. The Arch Cape post office, established in 1912, has ZIP code 97102. The community was named for a natural arch in the coastal rocks.
Postcard of Arch Rock in 1898. Arch Rock is a geologic formation on Mackinac Island in Michigan. It is a natural limestone arch formed during the Nipissing post-glacial period, a period of high Lake Huron levels following the end of the Wisconsin glaciation. To this day Arch Rock stands on the Lake Huron shoreline 146 feet (45 m) above the water. Limestone breccia is not an ideal material for natural bridges, and this type of formation is quite rare in the North American Great Lakes region.