Stalagmite vs. Stalactite: How to Tell the Difference Between These Cave Formations

Some of the coolest and spookiest-looking formations in caves are stalagmites and stalactites. They’re both formed through mineral-laden water dripping through cracks in a cave roof. However, they have one key difference: one hangs from the ceiling and the other rises up from the floor. But with such similar names, how can you tell them apart? We’ve got a couple of simple memory tricks for you that will solve the problem once and for all. And while we’re at it, we’ll tell you some interesting things about how these rock formations develop. We’ll also cover other kinds of formations, tips on safety, and some of the best caving locations in the world.

How Do Caves Form?

Caves are natural underground chambers that can be formed in four ways:

• Molten lava flows cool on the surface, making a hard shell, while inside lava continues to flow out to lower ground or the ocean. This leaves behind hollow systems of lava tubes that can be quite large.
• Waves at the seashore wear away an area of softer stones more quickly than the harder minerals surrounding it, creating a cave.
• Rainwater seeps through cracks in rocks and erodes softer limestone or sandstone buried deep in the earth, forming underground aquifers. Over time, changes in the amount of precipitation, uplift of the land, or heavy use of groundwater empties these aquifers, leaving behind caves.
• Oil-eating bacteria, known as extremophiles, deep underground release hydrogen sulfide gas that mixes with oxygen in groundwater and forms highly corrosive sulfuric acid that dissolves limestone.

What Are Stalagmites and Stalactites?

Stalagmites and stalactites are both varieties of speleothems; that is, cave features that are gradually formed out of mineral deposits. They can take thousands of years to reach large sizes. The amount of rainfall and the temperature in the area are two important determinants of how fast they will grow. Lots of rain causes more drips, and higher temperatures accelerate the decay of plants and animals, putting more carbon dioxide into the soil.

How Do They Form?

They form when rainwater seeps down into the earth, picking up carbon dioxide as it runs through organic material like leaves and animal waste. This forms carbonic acid, a weak acid that dissolves calcite found in limestone. When a cave has formed, the dripping water releases carbon dioxide. The calcite in the water redeposits around the drip, forming an “icicle” of minerals. This is a stalactite.

Some of the water drips to the floor still carrying calcite. When this mineral is released on the ground, it gradually builds up into a stalagmite that mirrors the stalactite above it. If the two meet, or if a stalactite grows long enough to reach the ground by itself, the resulting column is called a “stalagnate.”

Oh no, we just gave you a third hard-to-remember word! Ok, with no further delay, here are the memory devices you need to distinguish between these terms:

Memory Devices

Here are some simple ways to remember the difference between stalagmites and stalactites, and now stalagnates as well:

• Stalactites hold on “tight” to the ceiling. And their name has a “T” for “top.”
• Stalagmites stand up “mighty” and tall on the floor. And they have a “G” for “ground” in their name.
• Stalagnates look “stagnant” or completely formed (even though they are still growing).

Other Kinds of Speleothems

Stalagmites and stalactites are not the only kinds of speleothems you can find in caves. Mineral formations can come in all different shapes and patterns depending on how much water forms them and how it flows. For example, does it drip slowly, seep and run down a wall, condense from the air, hit the floor and splash, or create underground ponds? They also come in different colors depending on the exact mineral content of the water. They can come in shades of brown, red, orange, black, and white. Here are some examples of the wide range of interesting speleothems you can look for if you explore a cave:

• Dripstone – This includes stalactites and stalagmites but can come in different shapes described as looking like curly fries, soda straws, ribbons, clumps of worms, chandeliers, and fried eggs.
• Flowstone – This is a sheetlike deposit on cave walls and floors. It can look like thin curtains hanging from the ceiling, undulating thin bands of alternating colors described as “bacon,” and stone cascades that look like frozen waterfalls.
• Cave crystals – These are crystal-like formations with names like frostwork and moonmilk that evoke their mystical appearance.
• Cave popcorn or cave coral – These are knob-like chunks of calcite that resemble popcorn.
• Cave pearls – These almost perfectly round balls of calcium carbonate have rolled around by dripping water as they form.
• Calcite rafts – Rafts are a thin frosting of calcite that develops on the surface of cave pools.

Caving Tips

Easy Walking Tour Caves

Caves can be dangerous environments even if you are visiting a tourist attraction that guides thousands of visitors a year along well-marked passages. If you’re not attentive and careful, you can easily injure yourself. If visiting an easy walk-through tourist site, investigate in advance and wear proper footwear and clothing, remembering that caves can be quite cold even on the hottest summer day. Pay attention and follow all safety instructions. Do not run or jump in a cave. Don’t touch any of the mineral formations, as this can introduce bacteria and change the chemical content, altering development and leaving flaws. And be careful to take everything you brought back out with you.

Easy and Advanced Spelunking Caves

In contrast to touring a cave attraction, spelunking (or caving) is an adventure sport that will get you crawling on your belly through some low overhangs and squeezing through some claustrophobically tight spaces. Only attempt this under the guidance of someone experienced, knowledgeable, responsible, and safety conscious. And ideally larger than you! If they can get through a tight space, you can too! Communicate with your group leader if you are feeling uncomfortable or tiring. The leader might be able to guide the group on an alternate route that is less strenuous or gets you back a little earlier.

Safety

Here are some other cave safety tips from the U.S. Forest Service:

• Safety in numbers: Always go caving in groups of four to eight. If there is an injury, someone should stay with the injured and the others should go for help.
• Share your plans: tell one or more people at home where you are going and when you will get back. Stick to that plan, and if you do not return within six hours of the expected time, those at home should call the Forest Service or the police so a rescue operation can begin.
• Dress for success: make sure everyone is wearing ankle-high hiking boots, gloves, knee and elbow pads. Wear layers of clothing, along with a hard hat with a chin strap and light.
• Bring the right stuff: in addition to a helmet light, each person should have a couple of waterproof flashlights and plenty of spare batteries, as well as candles and matches in a waterproof case. Don’t forget a first-aid kit. Bring more than enough bottled water and high-energy foods, like energy bars, in waterproof bags.

Where in the U.S. Can You Explore Caves?

Here is a list of caves you can explore, with experiences for people of all ages.

1. Carlsbad Caverns – Carlsbad, New Mexico
2. Fantastic Caverns – Springfield, Missouri
3. Kazumura Cave – Hawaii
4. Lava Beds National Monument – Tulelake, California
5. Luray Caverns – Luray, Virginia
6. Mammoth Cave – Brownsville, Kentucky
7. Meramec Caverns – Stanton Missouri
8. Moaning Cavern – Vallecito, California
9. Ruby Falls Haunted Cavern – Chattanooga, Tennessee
10. Wind Cave National Park – South Dakota

Pick a cave for your next vacation and see if you can find stalagmites and stalactites, along with some cave bacon and popcorn while you’re at it!