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

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

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.

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.

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.

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

Types of Stalactites Types of Stalactites Icicle Straw Drape

Types of Stalagmites Dish Stack Fir Cone

Others

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

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

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

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

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

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

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

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

Caves form above, at, and below the GWT

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

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)

Hot Springs Paint Pot

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.

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)

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