Take a trip around the planet and you’ll come across incredible landscapes, from towering stone arches to massive canyons. These amazing rock formations exist because Earth is constantly changing. The shifting of tectonic plates, giant slabs of rock that form Earth’s surface, can make mountains. Wind and water can sculpt stones into unusual shapes.

All types of rock formations have something in common. They formed over very long periods of time. “Rocks are fascinating because they tell the story of Earth’s history,” says Michele Koppes, an earth scientist at the University of British Columbia.

Here’s what five unusual rock formations around the world reveal about our planet’s past.

Legend says this group of dark rock columns in Northern Ireland, known as Giant’s Causeway, was made by a giant named Finn McCool. But scientists know the real creator: volcanoes. The columns are made of an igneous rock called basalt.

Between 60 million and 55 million years ago, multiple eruptions covered the area with more than 600 meters (1,970 feet) of lava. When lava cools, it contracts. If it cools very slowly, the rock can crack, forming six-sided columns. “Mud in a puddle drying out on a hot day will form very similar patterns,” says park ranger Cliff Henry. “It all has to do with physics.”

Over time, erosion by ice and seawater exposed the columns. The landscape often surprises visitors. “Some people don’t believe it’s natural; they think it’s human-made,” says Henry.

This arch soars 14 meters (46 feet) above ground. It’s one of more than 2,000 rock arches at Arches National Park in Utah. The arches are made of sandstone, a type of sedimentary rock.

Between 220 million and 165 million years ago, the area was covered with giant sand dunes. Over time, the sand grains were pressed together. Minerals glued the grains into stone. The arches formed when water dissolved the minerals inside the softer sandstone. That caused the rock to crumble, carving the harder sandstone into bridge-like shapes.

Erosion is ongoing, says park ranger Lee Ferguson. New arches form—and collapse—all the time. Since the 1980s, the park has lost about 50 arches. “The rocks are constantly changing,” Ferguson says.