The Action of Groundwater

1. The Action of Groundwater Earth Science Grade 8

2. Groundwater • The water that soaks into the ground and collects in pores is called groundwater. • Rocks have varying amounts of pore space. • If they allow water into them, they are called permeable. • If they do not allow water into them then they are called impermeable.

3. Groundwater • Groundwater will continue to go lower into the ground (by the force of gravity), until it reaches a layer of impermeable rock. • This acts like a dam, and the water does not move any further. • The water fills in all of the pore space of the permeable rocks.

4. Groundwater • A layer of rock that allows the water into it, and also allows the water to flow through it is called an aquifer. • A layer that is completely filled with water is called the zone of saturation. • The very top of this zone is called the water table. This location varies from place to place. • The area above this zone is called the zone of aeration. It is filled with air, except after a rain when the water moves through it on its way to the saturated layer.

5. Groundwater • If you were going to dig a well for your house, you would have to dig deep enough to reach the zone of saturation. Otherwise you would not always have water. • If too many people dig wells in similar locations, there is a chance the well would run dry-which means that there is no more water available.

6. Groundwater Diagram (Zone of aeration) (Lake) (Zone of saturation)

7. Groundwater • Most of the time you need a pump to get the water to the surface (from the zone of saturation). • A special case called an artesian well -there is no need for a pump. The water moves up by itself.

8. Aquifer and Artesian well

9. Groundwater • Sometimes the land dips low enough to reach the water table level. Water that flows to the surface here are called springs. • They are what feeds many of our rivers and lakes. If the land around those springs is heated (near a volcano or magma), they heat the water it becomes a hot spring.

10. Springs and Hot springs

11. Groundwater • A special type of Hot spring is one that erupts periodically. This is called a geyser. • The most famous of this type of hot spring is Old Faithful in Yelllowstone National Park. It shoots out nearly 12,000 gallons of water every 60-90 minutes.

12. Geysers Old Faithful, Yellowstone

13. Groundwater • As groundwater travels it will eat away at some of the softer rocks in the ground. Sometimes it can eat away so much of an area that it will create a cave. • Inside this area it is very cool and very wet. The walls constantly have moisture on them.

14. Caves

17. Groundwater • The water contains dissolved materials, which build up and form new mounds of rock • When they build up from the ground, they are called stalagmites. • When they hang from the ceiling, they are called stalactites. • Sometimes the two shall meet, which we call a column.

18. Stalactites, stalagmites, columns

20. Groundwater • If the cave becomes large enough or it is close enough to the surface, the land above it may become unstable. • If the cave collapses, it will create a sinkhole.

21. Sinkholes

22. Sinkholes

23. Sinkholes

24. How do pot holes form? video

25. Neshaminy Falls Picture by Bill Heasley