The Topic: 

Easier - A cave is a large hole. It may be underground, in the side of a hill or mountain, or under a cliff. A cavern is a large cave.
Caves are natural shelters. Animals often live in caves. A person who lives in a cave is called a cave dweller. During prehistoric times, cave dwellers painted pictures on the cave walls.
Harder - A cave is an underground hollow or passage that is formed when water runs through an area with enough force to dissolve or wear away rock. Over many years as the water evaporates and simply drips, it leaves tiny deposits of calcium carbonate (calcite). These drops form rock sculptures that look like icicles called stalactites and stalagmites. Stalactites hang from the ceiling and stalagmites form from the ground up. To remember the difference, stalactites have a 'c' in the word for 'ceiling' and stalagmites have a 'g' for 'ground.' If they come together in the center, they become columns.
Caves Theme Page from Gander Academy
This comprehensive website for caves includes cave types, animals and plants, cave uses, exploration of caves, cave features, teacher resources, and more.
Exploring Caves from the U.S. Geological Survey
This website describes the different types of caves, their care and protection, defines cave dwelling animals, and shows where caves are located in the U.S.
Underground World of Caves
This online class examines the geology and ecology of caves. The course also describes safe methods of cave exploration.
Virtual Cave
Browse the mineral wonders unique to the cave environment! Here are collected images from around the world, combined to generate an 'ideal' cave . . . one that contains an example of every major type of speleothem, or secondary mineral deposit.
Choose one or more of the following cave projects or activities.
Try Some Cave Fun. Try some cave activities at the Kentucky Caverns Student Activities and Cave of the Winds sites. You might also want to explore a cave at Pathways (Part of the Mysteries of the Caminos Reales ThinkQuest Project) to find a fictional treasure.
Create Your Own Cave Art. Check out some of the ancient cave art at sites like La grotte de Lascaux (move your pointer/flashlight), and Virtual Tour of Cave Painting. If you lived in a cave, what would you paint? Go to Ancient Cave Paintings and follow the directions to create your own cave art.
Virtual Tour. Explore the Virtual Cave, The Armchair Caver, Colossal Cave, Mulu, Limestone Pavement, and Ruby Falls Virtual Tour. Create your own cave tour using HyperStudio. Create a stack that contains examples of stalactites and stalagmites, columns, waterfalls, and other cool features.
Complete a Cave WebQuest. Follow the procedures at one of these webQuest sites: 
1) Bats,Bats, Everywhere
2) Bat WebQuest (Grade 2)
3) Cave Art by C. Royal (Grade 6)
4) Cave Exploration in Wisconsin (Grade 4)
5) Going Batty by N. Cope
6) Spelunking Fun!!
Write A Cave Story. After learning about caves, write your own story about a cave. Illustrate it with your own artwork. Share it with friends.
Complete An Online Cave Course. Go to the Underground World of Caves and study the geology and ecology of caves and safe methods of cave exploration.
Website By Kids For Kids
Caves and Caverns ( 2001 Junior Project)
Learn about different types of caves, how caves are formed, cave creatures, and formations.
Goin' Batty
This site contains information and illustrations of all kinds of bats.
Lava Tube Caves Near Bend, Oregon
Learn about cave exploration, safety, formations, and lots more at this site by fourth grade students in Oregon.
Spelunking Wonderland: Caves, Caverns, and Crevices
(2000 ThinkQuest Junior Project)
This website takes visitors on visits to a variety of U.S. caves and caverns as well as some abroad. Explore the different natural formations and animal life that live there.
Underground in the Deep and Dark (1998 ThinkQuest Junior Project)
This site covers caving, and tunnels.
More Websites on Caves
Armchair Caver
Explore clickable maps that link to photographs of the cave. The maps are just hand drawn and don't show all passages.
Biospeleology from the Illinois Natural History Survey
Within caves a diverse biota may be found, exhibiting varying degrees of adaptation to the subterranean environment. Here you find information and links about cave habitats and fauna, as well as cave protection and related topics.
Cave Dwellers
Learn more about cave dwellers, a term used to designate ancient people who occupied caves in various parts of the world.
Cave of the Winds
The site includes cave terms, a full glossary with pictures as well as a cave quiz and bat quiz!
Caving by G. Baddeley
This site contains a small collection of articles and papers on caving, photographs, and links to some other caving resources.
Conservation Goes Underground by R. Johnson and M. McGimsey
This article reminds us that caves have unique rock formations, fragile species of wildlife, and cool, clear, flowing waters . . . all needing protection.
Expedition Rescue Guide from the Oxford University Cave Club
This is the site of a brief online guide to carrying out a cave rescue.
Formation of Caves at Kentucky Caverns
Here you learn how caves are formed.
Related Websites:
2) Cave Ecology
3) Caver's Glossary and Tips
4) Formation of Caves by J. Stanley
5) How Caves in This Area Were Formed from Mammoth Cave Online
6) Glossary of Cave Terms from Mammoth Cave Online
Glossary of Speleological and Caving Terms Australian Speleological Federation Inc.
This Australian caving glossary was developed form the earlier publications of J.N. Jenninngs (1960, 1985) and M.G. Meth (1998).
Limestone Pavement
Find the cave entrance, click and enter for a brief fun trip into a cave in the potholing region of North Yorkshire.
National Speleological Society
This is the comprehensive website of an organization dedicated to cave study, conservation, and exploration.
Related Websites:
2) Wisconsin Speleological Society
Our Caves and Subterranean Habitats from Oakland Museum of California
Take an online tour of sea caves, mud caves, lava tubes, talus caves, and wind caves.
Visit Online Caves
Caves of the Kingdom of Saudia Arabia
Here you can view cool reports and pictures of the caves of the Saudi Arabian desert.
Kartchner Caverns State Park
Kartchner Caverns State Park is a wet 'live' cave where water still percolates from the surface and calcium carbonate features are still growing.
Kungur Ice Cave
Learn about a legendary cave whose known passages stretch under the ground for over 6000 meters. This is only the part which has already been explored. To this day old slides and crumblings make it unsafe to determine the total length of the passages.
La grotte de Lascaux (Cave of Lascaux (French) (English)
Take a virtual tour of this cave in the Pyrenees renowned for more than 1500 Paleolithic paintings on the walls.
Related Cave Painting Websites:
2) Cave of Chauvet-Pont-d'Arc
3) Paleolithic Painted Cave of Lascaux
4) Lascaux: A Virtual Reality Installation 
5) Virtual Tour of Cave Painting
Murciélagos que viven en España (In Spanish)
Explore the caves of Spain and learn about bats. Identify different species. Find out why they live in the caves, and how they are protected by law.
Park Geology of Cave and Karst Parks (National Park Service)
This page lists parks that have a common geologic theme (caves) and links to webpages about each park's geologic features
Related NPS Website:
2) Cave and Karst Resources
Ruby Falls Virtual Tour
Here you find information on caves and how they form.
Related Webpage:
2) Geology
Cave Creature Websites
All About Bats! by K. Mitchell/
This website has information, activities, and lesson plans on bats.
Other Bat Sites:
2) Bats
3) Bats from Jaguar Paw
4) Bats, Bats Everywhere
5) The Bat Cave
6) Bat Conservation International
7) Fun Facts About Bats
8) Introduction to Bats from U.S. Fish & Wildlife Service
9) Let's Learn About Bats from Riverdeep
Bats at Collossal Cave Mountain Park, Tucson, Arizona
Colossal Cave Mountain Park serves as home or way station to almost half the bat species found in the state of Arizona, including some rare and threatened ones.
Other Sites on Cave Bats:
2) The Bat Cave
3) Bats Bats Everywhere
See also Creatures of the Night
Blind Creatures from Cool Fact of the Day
Here you learn about animals that spend their entire lives in underground caves, living in complete darkness.
Similar Websites:
2) Cave Critters
3) Biospeleology
Websites For Teachers
About Bats, Caves, & Deserts from the National Park Service
Here is the teachers guide (Go to Teacherguide) to Carlsbad Caverns National Park.
Caves (Grade 4)
This lesson plan has some built-in resources and a classroom activity.
Exploring Caves from the U.S. Geological Survey (Grades K-3)
This site contains lesson plans and activities for learning about caves.
Goin' Batty! (Grade K)
Here is an extensive plan for a unit on bats.
Other Bat Lessons and Activities:
2) Bats - Helpful Creatures of the Night (Grade 3) from Access Indiana's Teaching
Learning Center
3) Thematic Lesson on Bats (Grade K-3) by K. Mitchell and B. Parker
Lessons from Environmental Education Committee (EEC), National Speleological Society
Here is a collection of lesson plans.
Student Activities at Kentucky Caverns
Here are several lesson plans for caves.
cave dweller
cave painting
carbon dioxide
carbonic acid
cave coral
soda straw
'show cave'
gypsum flower
sea cave
lava cave
ice cave
sandstone cave
'creatures of the night"
blind crayfish
cave beetle
cave salamander
camel backed cricket
karst topography
lava tube
Created by Annette Lamb and Larry Johnson, Updated by Nancy Smith, 9/01.