They just might not be hexagons… instead of 6, they might have 5 or 7 sides, or a more irregular shape. But this cracking isn’t always random. In this case, the lava starts to crack into regular shapes. It’s due to a physical process that can happen in melted lava rock as it cools. Have a different answer or more to add to this one?

As it cools, it needs to shrink a bit, as hot materials usually take up more space than cooler ones.

Most areas within Earth'… These stones along Cape Stolbchaty, Russia, may look like they were put here on purpose, but they are actually the tops of columns formed from cooling lava. Image of Reynisfjara beach basalt columns by Karla Moeller. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill. Additional images via Wikimedia Commons. Basalt is primarily formed by the extrusion of lava flows onto the surface of the earth during a volcanic eruption.


Scientists, teachers, writers, illustrators, and translators are all important to the program. Cape Stolbchaty image by Екатерина Васягина. You’ve been walking on the bubbly rocks of an old lava flow for what seems like miles. These chunks begin to form at the top layer of the lava, which is cooling the fastest. You just might find some sculptures that were made by nature through the heating and cooling of melted rock. The intrusion of a narrow sill or igneous dike below the crust also results in the formation of basalt. This is how really tall cylinders can form. It has long lines—columns of rock that look at least 30 feet tall, stacked alongside one another.

That means it is more likely it will cool into hexagonal chunks.

Though the rocks under your feet change in color and shape, many look similar… small, worn, and full of tiny pockets. By volunteering, or simply sending us feedback on the site. Imagine a huge flow of hot, liquid magma that is settling.

Scientists also think that faster cooling, like when lava is exposed to water, may also help with the formation of these columns. The more uniform the material of the lava is (or basically how smooth and well mixed it is), the more evenly those centers pull. You are looking at a type of formation called columnar jointing.
Community Solutions. And even when the material is a bit irregular, these cylinders can still form. As lower levels of the lava start to cool, they are also pulled into the shape under each center. Because of this shrinking, the surface of the lava starts to crack. How do these basalt columns form? Basalt columns have formed in many places around the world that have a lot of volcanic activity. The difference between basalt and gabbro is that basalt is a fine-grained rock while gabbro is a coarse-grained rock. The outer layer is starting to cool and darken in color from orange to black. More than 90% of all volcanic rock on Earth is basalt, and the eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Public Service and These columns of rock are most likely a volcanic rock called basalt.

If you are interested in helping with the website we have a volunteers page to get the process started. Devil’s Tower, in Wyoming (USA), is a good example. It usually begins to shape from the top down into the middle or even bottom of the lava flow. And rock columns also aren't limited to Earth... rock columns have even been found on Mars. They are well-known in certain places like Iceland, Ireland, and the United States (such as at the Devil’s Postpile monument in California), but they are found in many, many more countries across the world.