"Caves" Changes in Ground Form PPT Courseware

"Caves" Changes in Ground Form PPT Courseware

Cave landscape features

There are various accumulation forms, such as stalactites, stalagmites, stone pillars, stone mantles, etc.

Thinking: Why are there caves in mountains made of limestone?

1. Experimental equipment:

Dropper Dilute hydrochloric acid Limestone

2. Precautions

1. Hydrochloric acid should not get on your hands or splash on your body.

2. When observing the rocks after dropping acid, do not touch them with your hands.

3. Experimental methods

Use a dropper to add a few drops of dilute hydrochloric acid to the limestone.

4. What happened? What do these phenomena indicate?

There is more rain in the south. When the rain falls, it often absorbs carbon dioxide from the air and soil and becomes acidic. When acidic rainwater seeps into underground limestone cracks, what impact will it have on the limestone?

How will rocks made of limestone change over time?

When natural rain falls, it often absorbs carbon dioxide from the air and soil and becomes acidic. When these acidic rainwater seeps into the cracks in the underground limestone, it will dissolve the limestone. Over time, many caves will be formed in the rock formations made of limestone, and they will be connected to each other and continue to expand. Once the groundwater receded, wonderful caves formed in the limestone mountains.

Question: Why are there stalactites hanging from the top of the cave?

(Read the experimental process patiently and carefully and fill in the record sheet)

1. Experimental equipment: beaker, clarified lime water, straw

2. Experimental process:

1. What happens when you blow air into clear lime water? (Record the blowing time and fill in the record sheet).

2. Continue to blow, what else happens? (Record the blowing time again and complete the record sheet).

3. After letting it sit for a while, what did you find at the bottom of the cup? (Fill in the experiment record sheet).

Limestone in nature (the small white particles in the turbid "lime water" are the materials that make up limestone), after encountering rainwater or groundwater containing carbon dioxide, it slowly becomes like the water that became clear for the second time in the experiment. This When the seed water seeps into the top of the cave and drips down, due to changes in temperature and pressure, milky white precipitates remain on the top of the cave. Over time, more and more will accumulate and the drops will grow longer, forming stalactites.

Make a bold guess: How are stalagmites and stone pillars formed?

In a karst cave, when water containing dissolved limestone material drips from the top of the cave, due to changes in temperature, the generated water evaporates and carbon dioxide escapes, causing the material in the water to precipitate and gradually increase in size from top to bottom to form stalactites.

Stalagmites are formed when water containing dissolved limestone material drips from the cave roof or stalactites to the cave bottom. The water evaporates, carbon dioxide escapes, calcium carbonate precipitates, and gradually grows from bottom to top.

What about the stone pillars?

Where's the stone flower?

china cave

1. Formation:

Fissure erosion of soluble rocks dissolved in groundwater. Underground cavities expanded by dissolution.

2. Distribution characteristics:

It is widely distributed in both north and south, but concentrated in the south, especially in the hills of Guangdong and Guangxi and the Yunnan-Guizhou Plateau.

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