When tropical storm systems barrel across the Atlantic Ocean toward North America, they often take aim at the Lesser Antilles—an arc of small islands that marks the eastern boundary of the Caribbean Sea. In fact, the islands often are the first thing forecasters talk about when a tropical system heads our way.

The Lesser Antilles arc from the U.S. Virgin Islands, near Puerto Rico, all the way down to South America. They comprise three separate groups: the Leeward Islands, the Windward Islands, and the Leeward Antilles. The Windwards extend farthest into the Atlantic. They were the first stop for European sailing ships, which followed the prevailing winds to the Americas.

Most of the islands are volcanic. They formed as two of the plates that make up Earth’s crust plunged below the Caribbean Plate. As the rock descended, it melted. Some of the molten rock then forced its way upward, building the islands.

Earthquakes rock some of the islands. And some of the volcanoes that built the islands are still active. A massive eruption that began in 1995, for example, destroyed the capital of the island of Montserrat, and forced most of the population to leave the island.

Despite the volcanoes and hurricanes, many of the individual islands are popular tourist sites. Places like the Virgin Islands, Aruba, and Martinique offer tropical beaches, coral reefs, rugged mountains, and other natural attractions—at the edge of the Caribbean Sea.