What is a cave?
A cave is an area or space under the surface of the Earth, in hillsides, or in cliff walls. Most of the time, caves are a complicated system of connected underground passageways. It’s kind of like an underground maze.
How are caves formed?
It takes a long, long time for a cave to form because the natural processes that make a cave are very slow. These processes can include pressure, erosion from water, volcanoes, tectonic plate movements, chemical actions, and microorganisms.
Most caves are formed in rocks that can dissolve more easily like limestone, marble, dolomite, and gypsum.
Solutional caves are the most common, and they are formed from rainfall and chemical processes. When rain soaks into the Earth’s surface and carbon dioxide is released by dying plants into the soil, the water, and the carbon dioxide result in a chemical reaction that turns the water into carbonic acid.
Over time, the carbonic acid eats away at the rock and dissolves it, forming a cave passage. Most of these caves take more than 100, 000 years to grow big enough to fit a human.
Caves called lava tubes are formed when a volcano erupts and lava flows across Earth’s surface. The lava on the surface hardens and forms a solid roof, while the lava underground drains away, leaving an empty tube called a lava tube
Sea caves form when constant movement from waves and tides gradually weakens sea cliffs, eroding the rock and creating a cave.
What are some features of caves?
Rock formations called speleothems decorate most caves. Speleothems can hang down from the ceiling, sprout up from the ground, or cover the sides of a cave.
The speleothems that hang from the ceiling look like icicles and are called stalactites. They form from water dripping from the roof of the cave.
Stalagmites grow upward, and this is usually from water that dripped off the end of stalactites. Sometimes, stalactites and stalagmites join together in the middle, forming columns.
The sheets of calcite that cover some cave walls or even cave floors are called flowstones. Other rock formations include helictites, which form twisty shapes running in all directions.
These speleothems grow only an inch every 100 years, so you know that caves with large stalactites or stalagmites have been around for a long, long, long time.
Different Types of Cave Patterns
- Branchwork caves resemble surface dendritic stream patterns; they are made up of passages that join downstream as tributaries. Branchwork caves are the most common of cave patterns and are formed near sinkholes where groundwater recharge occurs.
- Angular network caves form from intersecting fissures of carbonate rock that have had fractures widened by chemical erosion. These fractures form high, narrow, straight passages that persist in widespread closed loops.
- Anastomotic caves largely resemble surface braided streams with their passages separating and then meeting further down drainage. They usually form along one bed or structure, and only rarely cross into upper or lower beds.
- Spongework caves are formed as solution cavities are joined by mixing of chemically diverse water. The cavities form a pattern that is three-dimensional and random, resembling a sponge.
- Ramiform caves form as irregular large rooms, galleries, and passages. These randomized three-dimensional rooms form from a rising water table that erodes the carbonate rock with hydrogen-sulfide enriched water.
What type of creatures lives in caves?
There are three types of cave life
- Trogloxenes - These are cave visitors. They come and go at will, but they use the cave for specific parts of their life cycles - hibernation, nesting or giving birth. A trogloxene will never spend a complete life cycle in a cave and they have no special adaptations to the cave environment. The most familiar trogloxenes are bats, bears, skunks, and raccoons.
- Troglophiles - These are animals that can survive outside the cave, but may prefer to live inside it. They leave the cave only in search of food. Some examples of troglophiles are worms, beetles, frogs, salamanders, crickets and even some crustaceans like crayfish.
- Troglobites - They spend their entire life cycle within a cave. They're found only in caves and wouldn't be able to survive outside a cave. The troglobites are the animals that have adapted to cave life. They have poorly developed or absent eyes, little pigmentation and metabolisms that allow them to go a long time without food. They also have longer legs and antennae, allowing them to move and locate food more efficiently in the dark. Troglobites include cave fish, cave crayfish and shrimp, millipedes, as well as some insects.
Scientists who study caves are called speleologists, and they believe there are close to 50,000 different species of troglobites. Although new species are being discovered all the time, we will probably never discover them all.
Fun facts about caves
- Cave exploration is called caving, potholing, and spelunking.
- Humans have used caves throughout history for burial grounds, shelter, and religious sites. Ancient treasures and artifacts have been found in caves all over the world.
- The maximum depth a cave can reach underground is about 9800 feet (3000 meters). Beyond this point, the pressure from the rocks would become too great, and the cave would collapse.
- The deepest cave humans have discovered is the Voronya Cave in Georgia. It is 7208 feet (2197 meters) underground.
