What resources does a coastal city need?
Tulum is a walled city that was once inhabited by the Maya people. Tulum is on the Yucatan Peninsula of Mexico. The beautiful blue Caribbean supplied the Maya with abundant fish. What else would the Maya people have needed? Fresh water is found in cenotes, sinkholes that are common in the Yucatan limestone.
Some water soaks into the ground. It travels down through tiny holes in soil. It seeps through cracks in rock. The water moves slowly, pulled deeper and deeper by gravity. Water in an underground rock or sediment layer is groundwater. Underground water can also erode and deposit material.
Rainwater absorbs carbon dioxide (CO2) as it falls. The CO2 combines with water to form carbonic acid. The slightly acidic water is especially good at dissolving the rock limestone. Groundwater creates landforms by dissolving away rock.
Florida is unique for groundwater erosion. The state is extremely flat and is made mostly of limestone. Due to the wet climate, groundwater surfaces in many locations. In the Everglades, rivers create a wide floodplain and groundwater comes to the surface (See Figure below).
A cypress forest in Everglades National Park needs water to thrive.
Caves are one of the types of landforms created by groundwater erosion. Working slowly over many years, groundwater travels along small cracks. The water dissolves and carries away the solid rock. This gradually enlarges the cracks. Eventually, a cave, like the one seen in the Figure below may form.
Water flows through a limestone cave.
You can explore a fantastic cave, Kartchner Caverns, in Arizona, by watching this video: http://video.nationalgeographic.com/video/player/science/earth-sci/exploring-kartchner-sci.html.
As erosion by groundwater continues, the ceiling of a cave may collapse. The rock and soil above it sink into the ground. This forms a sinkhole on the surface. Some sinkholes are large enough to swallow up a home or several homes in a neighborhood.
groundwater: Fresh water that moves through pore spaces and fractures in soil and rock beneath the land surface.
sinkhole: Circular hole in the ground that forms as the roof of a cave collapses.
- Groundwater erodes rock beneath the ground surface. Limestone is a carbonate and is most easily eroded.
- Groundwater dissolves minerals and carries the ions in solution.
- Groundwater erosion creates caves and sinkholes.
Use this resource to answer the questions that follow.
Kartchner Caverns State Park, Arizona at http://www.youtube.com/watch?v=uF75q4vzbAY (3:11)
- What is under Arizona?
- When were they discovered?
- When did this area become a state park?
- How long did it take the caverns to form?
- What makes caves interesting?
- How does groundwater erode rock?
- Why is groundwater acidic?
- How does a cave become a sinkhole?