Science Projects > Earth & Space Projects > Stalactites, Stalagmites, & Other Cave Features 

Stalactites, Stalagmites, & Other Cave Features

Cave formations

Caves are full of mineral deposits that form unique shapes, such as the icicle-like stalactites (which hang from the ceiling) and stalagmites (which rise up from the ground). Have you every wondered how they are formed? Learn about cave formations and then make your own!


Cave Features Science Lesson

If you’ve ever been inside an underground cave, you’ve probably seen many different rock formations.

Did you wonder what they were called or how they were formed?

The general name for cave features is speleothems. Cave features are usually formed by slow-moving water that has a high calcium carbonate content.

Chemical changes inside the cave make the minerals harden and form deposits, such as icicle-like stalactites (which hang from the ceiling) and stalagmites (which rise up from the ground).

Columns are created when a stalactite and stalagmite join together.

Cave pearls are smooth, rounded speleothems that form in shallow hollows where water drips.

Curtains are folded sheets of hardened mineral from the ceiling or wall of a cave, often so thin that they are translucent. Some of them look like large stone strips of bacon, while others look like sheets of long icicles.

Dripstone is the term for calcium carbonate deposits such as stalagmites, which were formed when water dripped through a point of aeration.

Flowstone is the term for mineral deposits that were formed by water flowing along the floor and sides of caves.

Other minerals, such as gypsum, also form deposits. When calcium carbonate crystallizes, it forms the minerals calcite and aragonite (also vaterite, which is less common).

Most caves are formed from limestone, a sedimentary rock made primarily of calcite.

Cave Features Science Project

Making Stalactites and Stalagmites

(Adult supervision recommended.)

What You Need:

What You Do:

1. Cut two 24′ pieces of cotton string or wool yarn, and tie one metal washer to each end to act as a weight.

2. Fill four small glass jars or beakers 2/3 full with very warm (120-140 °F) water. Stir in as much baking soda into two of the jars as will dissolve; do the same with Epsom salt in the other two jars. Put the jars in a warm place where they can sit undisturbed for about a week.

3. Next, place a small plate between each set of jars and put the ends of one string in the baking soda jars with the middle of the string draping in a ‘u’ shape just above the plate. Do the same with the Epsom salt.

After a few days, check to see if any material has built up on the string. An icicle-like formation should form downward on the string and upward on the plate.

Real stalagmites and stalactites are formed in almost the same way, by mineral-containing waters dripping in caves until a deposit of calcium carbonate builds up…or down, as the case may be.

Earth & Space Science

Welcome! Read other Earth & Space Science articles or explore the rest of the Resource Center, which consists of hundreds of free science articles!

Shop for Earth & Space Science Supplies!

Home Science Tools offers a wide variety of earth science products and kits. Find earth science products and space educational supplies for labs and classrooms.

Related Articles

Cloud Types Worksheet

Cloud Types Worksheet

Use this Cloud Types Worksheet with the "Types of Clouds" Science Lesson to review the basic types of clouds and what kind of weather they bring. Find weather science projects here and here.

Solar Energy Matching Game

Solar Energy Matching Game

Print out this page on a sheet of heavy paper or cardstock. Kids can color the pictures and cut out the squares to make a matching game. Half of the squares show a way to use solar energy as an alternative to the picture shown on the other squares. Place all the...

Simple Spring Break Science Projects

Simple Spring Break Science Projects

Spring break is here! What will you do with your time off? Perhaps you're looking forward to a family vacation, or a few days of down time at home. Either way, find a quick and easy project that's sure to put a sparkle in the eye of any science lover, or win over a...

should I learn computer coding