1. Caves
A cave is defined as an underground passage large enough for a person to crawl into, naturally formed, and in complete darkness.

2. Geologic work of groundwater
Karst topography
Landscapes that have been shaped by the dissolving power of groundwater on limestone
Some common features include
Irregular terrain
Dolines: Sinkholes or sinks (formed by groundwater slowly dissolving the bedrock
often accompanied by collapse
Disappearing (aka sinking) streams

3. Karst Topography
Rocks are dissolved by water: surface water or groundwater.
Carbonates, limestone, and dolostone are dissolved by acidic water.
Evaporites, rock salt, and gypsum are dissolved by water.

4. How does a cave form? Rain dissolves Carbon Dioxide into Carbonic acid
Carbonic acid dissolves minerals in rock
Rock is sculpted in weak spots
Water seeps through rocks and makes underground waterways
When the water level drops, the waterway exits the rock through the exiting hole (resurgence)
Collections of water creates deep gaps in caves.
When the water level outside the cave drops, the cave empties and dries out.

6. Stalactites Stalactites
Formed by water that drops from the top of the cave that contains calcite
The calcite is left when the water drops
Constant winds blowing cause stalactites to grow in crooked.
Occasionally, stalactites will grow together with the stalagmites and will create a column.

7. Stalagmites Stalagmites: Form from the bottom of the cave
They grow about 1 cm every 1000 years because it is hard for water to evaporate in the moist cave

8. Types of Stalactites
Types of
Stalactites
Icicle Straw Drape

9. Types of Stalagmites
Dish Stack Fir Cone

10. Others

11. Types of Caves
Erosional- formed by the action of water or wind, carrying abrasive particles capable of carving rock

12. Types of Caves
Lava Tube- lava travels beneath the surface and is expelled by a volcano during an eruption

13. Types of Caves
Sea Caves- form from wave actions along the coast where areas are weak in sea cliffs

14. Types of Caves
Solution Caves- form where rock is dissolved away

15. Sinkholes
Groundwater dissolves soluble rock, creating fractures and caves.
Dissolving continues to form larger caves and fractures.

16. Dolines (Sinkholes, Cenotes )
Collapse sinkholes form when water level drops
Solution sinkholes due dissolution at surface

17. Winter Park sinkhole (1981)
100 m across
One day
Due to water table lowering
Now an urban lake.

18. Cenotes Yucatan, Florida
Flooded and dissolved during interglacial time (high sea-level)
They broke during glaciations
As the sea level dropped during active glaciation, the water table also dropped, leading to the drainage of caverns that were previously filled with water. This caused the ceilings of the caves to collapse

19. Caves form above, at, and below the GWT

20. Hot Springs, Geysers and Fumaroles
At a depth of about 20m, the temperature remains constant all year, and the water of a well or spring is close to the same
Below 20m, heat from the earth’s interior raises the temp. about 1°C for every 40m.
As a result, water from deep artesian wells or springs can be much warmer
Groundwater may also be warm in regions of recent volcanic activity, as the igneous rock is still hot enough to boil water

21. Hot Springs, Geysers and Fumaroles
Hot Springs occur where heated water comes to the surface
If hot water comes up through thick, sticky clays, a sputtering spring called a paint pot results (also called a mud volcano)
Geysers are boiling hot springs that periodically erupt and gush hot water and steam (eg. Old Faithful in Yellowstone National Park)

22. Hot Springs
Paint Pot

23. Hot Springs, Geysers and Fumaroles
Geysers tend to have constricted tubes, so the water at the bottom is under pressure, and once it develops steam, it forces superheated water up to the surface.

24. Water Hardness
Hard water contains a substantial amount of dissolved minerals (ions), usually calcium, magnesium or iron.
Water hardness interferes with its uses, for example it will not form soap suds well and forms scale in water pipes etc.
Hard water occurs in areas that have limestone bedrock, due to dissolved calcium (from calcite)

25. Mineral Springs
Sometimes a spring contains so much dissolved mineral matter that it cannot be used for ordinary drinking or washing
This is called a mineral spring (sometimes these are used as health resorts/spas)
Water from hot springs usually has a high mineral content because hot water dissolves minerals better than cold