Different Kinds Of Cave Formations

Ever heard of a cave?

Yeah, they’re a pretty underground thing. 

(hah!)

From mountains to valleys to glaciers, ocean-side cliffs, volcanoes and more, caves are naturally-occurring caverns that are found all over the world and contain plenty of ancient wonders. 

Here are the different kinds of caves, what they’re made from and, of course, how they get there in the first place!

Types of caves and how they’re made

Solution caves

Solution caves are the types of caves most people think of when picturing an underground cavern — a damp, musty space deep underground with stalagmites, stalactites, bats and the like.

These caves (also known as karst caves) are formed from chemical reactions between the rocks and the groundwater in a process known as dissolution. Thus, the term “solution” caves. Only certain kinds of rock allow for dissolution processes to occur, which is why you’ll only ever find solution caves in rock beds of carbonate and evaporite rocks, such as limestone, marble, dolomite, gypsum, anhydrite and halite. 

The process is slow but simple. Rain droplets absorb carbon dioxide (CO2) as they tumble down to Earth and soak into the ground, where it picks up even more CO2 and creates a slightly acidic water. This acidic water eventually enters groundwater systems and starts its journey down water systems and waterways through the rock. 

Dissolution occurs when that acidic water finds its way into cracks, craveasses and fractures in the rock. Once that happens, the chemical reactions between the acid and the carbon-rich rock cause the calcium and carbon bonds in the rock to break — dissolving the rock itself.

This process can happen slowly over a period of time or quickly (relatively quickly, at least) depending on the flow of water and the type of rock. Once the cavity is large enough for a human to fit inside, it’s classified as a cave!

Talus caves

Talus caves are cavities created by boulders or rocks falling on top of each other, usually as a result of landslides or avalanches. Water and snowmelt may help remove smaller rocks and debris, or it may fill the caves up with silt over time — it depends on where the caves are.

The talus caves in Pinnacles National Park in California are some of the more well-known talus caves, as many are large enough to explore and meander through!

Primary/lava caves

Primary caves are caves that are created at the same time as the rocks around it, so they are nearly always associated with lava tubes and lava caves. 

Lava caves are long, tube-like caves that travel in the direction of lava flows. As hot, molten lava travels down a slope or across the ground, the surface of the lava exposed to the air cools first and creates a crust over the hotter, faster-moving lava below. The lava cools from the top down in this way, with the crust getting thicker and thicker and the interior lava moving quickly through this tube. 

If the flow of lava is fast enough, eventually the hot lava on the inside will run out through the end of the tunnel instead of hardening inside it, leaving behind an empty lava tube!

The Ape Cave on Mount St. Helens in Washington is a popular lava tube that extends around 2.5 miles into the mountain!

Glacier caves

Sometimes called “ice caves” — through erroneously — these caves occur in glaciers where melted water carves out the soil and ice on its way out the glacier. 

Some of the most popular glacial caves in the United States are in the Wrangell - St Elias National Park and Preserve in Alaska, where ice caves are commonplace along the many ancient glaciers. You can also find some in Washington and Montana in the Cascade and Rocky Mountains.

Sea and littoral caves

You can find sea caves all over the world where ocean waves break onto rock or cliff faces. 

Unlike solution caves which are created via a chemical reaction in the rock, sea caves are purely a result of pure unadulterated force. As waves crash into cliff faces, the force of the water shoves water and air into cracks in the rock and weaken the structural integrity of the cliff. Over time, pieces of the rock chip away and break off to create larger and larger cavities.

These sea caves also occur around lakes that are large enough to have waves (like the Great Lakes, for example), though they are called littoral caves. The caves along the Pictured Rocks National Lakeshore in Michigan is an example of sea caves on a lake!

Eolian caves

Eolian caves are caves made by wind, rather than by water. 

These caves usually occur in deserts and other dry regions where there is loose, dry sand and high winds. 

Wind picks up loose particles of sand and dirt and slams them into rock faces. Over time, the constant pummeling of sand on the rocks chip away at the sediment and leave cavities in the rock, especially in cliffs or valleys where the wind patterns are regular and rarely change direction. These caves aren’t quite as cavernous as, say, glacier caves or solution caves, but they are still often used by human civilizations for housing and shelter. 

In fact, some of the more popular eolian caves are the caves in Mesa Verde National Park, which contain cliff dwellings built by Ancestral Pueblans in the late 12th century. 

Next time you have a chance to explore a cave, be sure to check out the landscape around it to get some clues as to how the cave was formed! If walls could talk, what do you think those ancient caverns would say after all those years buried far from the surface?

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Featured photo courtesy Pixabay/juanguzmanphoto