Caves are mysterious and beautiful places that offer a fascinating glimpse into the Earth’s hidden world. One of the most striking features of many caves are the formations called speleothems. These are mineral formations created by the deposition of minerals from water as it drips or flows through caves over thousands or millions of years. For beginners interested in caving or speleology (the study of caves), understanding the different types of speleothems you might encounter is an exciting part of the adventure.
In this blog post, we’ll introduce you to some of the most common types of speleothems found in caves, explaining what they look like and how they form.
What Are Speleothems?
Speleothems are formations made from minerals, usually calcium carbonate, which is the main mineral in limestone. When water seeps through rock or drips from the cave ceiling, it picks up minerals from the surrounding rock. As the water moves through the cave, it eventually evaporates, leaving behind these mineral deposits that build up over time. The mineral deposits form different shapes and structures depending on the flow of water and the environment inside the cave.
Now, let’s explore some of the most common speleothems you can find in caves.
1. Stalactites
What They Are: Stalactites are icicle-shaped formations that hang from the ceiling of a cave. They are typically formed when mineral-rich water drips from the roof and evaporates, leaving behind layers of minerals.
How They Form: As water drips from the ceiling, it leaves behind small deposits of calcium carbonate. Over time, these deposits build up and form long, pointed structures that hang down. Stalactites can vary in size, from tiny formations just a few inches long to enormous ones several feet long.
Fun Fact: The word “stalactite” comes from the Greek word stalaktos, meaning “dripping” or “that which drips.”
2. Stalagmites
What They Are: Stalagmites are formations that rise from the ground of the cave, often directly beneath a stalactite. They are similar to stalactites, but instead of hanging from the ceiling, they grow upward.
How They Form: Stalagmites form when the water dripping from the ceiling hits the ground and leaves behind a deposit of minerals. Over time, this builds up into a mound or tower-shaped structure. Like stalactites, stalagmites can grow to impressive sizes if they are left undisturbed for long periods.
Fun Fact: The word “stalagmite” comes from the Greek word stalagma, meaning “a drop” or “dripping,” reflecting how these formations grow from the mineral deposits left by drips of water.
3. Columns
What They Are: Columns are large, vertical formations that form when a stalactite and a stalagmite grow together and merge.
How They Form: If both a stalactite (hanging from the ceiling) and a stalagmite (growing from the ground) continue to grow toward each other over thousands of years, they can eventually meet and form a column. This process happens very slowly, and the result is a solid, often massive column of mineral deposits.
Fun Fact: Columns are often the most impressive speleothems in large caves, and some can be very thick and tall—sometimes even wider than a person!
4. Flowstone
What It Is: Flowstone is a smooth, sheet-like formation that covers the walls, floors, or ceilings of a cave. It looks like flowing water, with layers of mineral deposits that have formed from continuous water flow over a surface.
How It Forms: Flowstone forms when water flows across a surface and deposits minerals over a wide area. As the water flows, it leaves behind thin layers of mineral deposits that accumulate over time, creating a smooth, often shiny surface.
Fun Fact: Flowstone can come in a variety of colors, ranging from white and cream to reddish-brown, depending on the minerals in the water.
5. Helictites
What They Are: Helictites are small, twisting, and curving speleothems that often grow in odd, unpredictable directions, sometimes at odd angles or even against gravity.
How They Form: Helictites form when water moves through the cave in a very slow and steady way. The water is supersaturated with minerals, and as it travels, it deposits them in a twisting pattern. Unlike stalactites and stalagmites, helictites grow in all sorts of directions due to the forces of capillary action and air movement.
Fun Fact: Helictites are often considered one of the most unusual and delicate speleothems because of their random and intricate shapes.
6. Cave Pearls
What They Are: Cave pearls are small, smooth, spherical formations found on the floors of caves. They resemble tiny, polished pearls and are often found in pools of water.
How They Form: Cave pearls form when mineral-rich water flows over a small pebble or speck of dirt. Over time, the water continues to deposit minerals around the object, gradually building up layers that create a smooth, round shape. Cave pearls are often found in areas with slow-moving or still water, where the minerals can build up evenly.
Fun Fact: Some cave pearls can be so smooth and shiny that they resemble real pearls, which makes them an interesting find for cavers.
7. Travertine
What It Is: Travertine is a type of flowstone that is often found in caves and other limestone-rich environments. It forms as a hard, dense rock and has a distinct appearance with layered, banded patterns.
How It Forms: Travertine forms when mineral-rich water, usually containing calcium carbonate, is deposited on a surface, such as a cave floor or wall. The water’s evaporation leaves behind a smooth, polished, and sometimes porous rock that can build up in layers.
Fun Fact: Travertine is often used in construction and decoration, and some of the most famous examples, like the famous White House in the United States, are made from travertine stone.
8. Moonmilk
What It Is: Moonmilk is a soft, creamy, white substance found on cave walls and ceilings. It has a chalky texture and a smooth, sometimes even velvety appearance.
How It Forms: Moonmilk forms when water evaporates in a cave, leaving behind fine mineral deposits. It is often made of a mixture of calcium carbonate and clay minerals, creating a soft, powdery substance. The term “moonmilk” is used because of its milky-white color and smooth texture.
Fun Fact: Moonmilk can be found in caves with very specific conditions, often where the cave’s humidity is high and the air is still.
Conclusion
Caves are home to some of the most unique and awe-inspiring formations on Earth, and understanding speleothems is a great way to appreciate the beauty and complexity of these underground worlds. Whether you’re admiring the delicate, twisting shapes of helictites, marveling at the grandeur of a cave column, or exploring the smooth, reflective surfaces of flowstone, speleothems provide a glimpse into the slow, fascinating processes that shape our planet.
As a beginner caver or nature lover, the next time you visit a cave, take a moment to appreciate the speleothems that surround you—each one is a testament to the Earth’s natural artistry, sculpted over millennia.
No responses yet