EARTH SCIENCE 11 CHAPTER 9 NOTES WATER MOVING UNDERGROUND

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1 EARTH SCIENCE 11 CHAPTER 9 NOTES WATER MOVING UNDERGROUND KEY A. ALL THE WORLD S WATER 1. The world has an estimated one and one third thousand million cubic kilometers of water. 2. The earth s water is distributed as follows: SALT water (oceans) 97% FRESH water 3% - ice (glaciers) = 2½% - ground water = 3/8% - surface water (lakes, rivers, streams) = 1/8% B. THE WATER CYCLE (see diagram page 6) 1. The water or HYDROLOGIC cycle is the continuous cycle of water. 2. SUNLIGHT provides the energy for evaporation of water vapor from the ocean. Not all the water vapor comes from the ocean. Sometimes from other places. 3. The water vapor is carried by WIND and condensed and falls back to the earth s surface. 4. Some water returns to the oceans and some rivers and lakes as a result. Some gets into the ground to become GROUND WATER. Some water is EVAPORATED and some is TRANSPIRED back into the air. 5. Transpiration is the process by which LEAVES OF PLANTS give off water vapor. 6. EVAPOTRANSPIRATION is the combination of evaporation and transpiration. 7. When the RUN OFF reaches the ocean, one cycle has been complete. There are other routes to take. Know how to diagram the water cycle. C. THE WATER BUDGET 1. Budget is a statement of expected INCOMES and expected OUTGO. In a balanced budget both are equal. 2. The water budget income is PRECIPITATION and the outgo is RUNOFF and evapotranspiration. 3. Canada s average income is 730mm (annual). Its outgo is 730mm. 4. Only 52% of the water returns to the air by evapotranspiration and the 48% that comes from the ocean is returned by RUNOFF.

2 2 D. INDIVIDUAL WATER BUDGETS 1. Each LOCALITY OR REGION has its own water budget because they vary so drastically. 2. There are many factors that determine where the water goes. a) CLIMATE - hot, dry -- 83% evaporates (prairies, summer) - cool, moist -- 22% evaporates (West Coast) b) RAINFALL DISTRIBUTION - heavy, downpour -- high % runoff - slow, steady -- low % runoff c) TYPE OF SOIL OR VEGETATION - steep, bare slopes -- high runoff - level porous soils, plants -- low runoff E. CAN ROCKS HOLD WATER? 1. Pores in rocks are simply the SPACES between the crystals or grains of the rock. 2. WELL-ROUNDED particles of gravel, sand or clay with little or no cement between grains may be 40% pore space. 3. The amount of space differs greatly, especially in sandstone. 4. Large deposits of gravel, sand or clay with no cement may be up to HALF pore space. 5. The % of pore space is LARGER where the particles are rounded and the same size. When the sizes are mixed the small particles fill the spaces where the water would have gone reducing the pore space. Angular pieces fight together and REDUCE pore spaces too. 6. Water is often retained in rocks with a LARGE % of pore space. F. CAN ROCKS TRANSMIT WATER? 1. The POROSITY of a rock indicates how much of its volume is open space. 2. Water will not pass through rocks easily if the pores are TINY (clay, shale). Water will pass through sediments or rocks with large pores spaces (sand, gravel, and maybe sandstone). 3. PERMEABILITY is the ability of rocks to transmit water. It is just as important as porosity. Permeability is important in the origin of springs and WELLS. 4. Permeable (water passes through easily) materials are sand, gravel and sandstone. Impermeable (water doesn t pass through easily) materials are clay, shale, and most igneous and metamorphic rocks. 5. Cracks can form in impermeable rock to make them PERMEABLE. (i.e. limestone)

3 3 G. FORMING THE WATER TABLE (see diagram last page) 1. When it rains water enters pores in the soil. If it continues to rain the water moves downward until it reaches an IMPERMEABLE material (clay, shale). The water starts to build up and rises higher and higher. 2. The part of the ground where all the pore spaces are filled with water is called the zone of SATURATION. 3. The surface of the saturation zone is the WATER TABLE. 4. The ground up above the water table is called the zone of AERATION. It has three parts: a) Just below the surface is the belt of SOIL WATER (water stuck to topsoil). b) Intermediate belt that is dry except during rains. c) CAPILLARY FRINGE - just above the water table where water rises from the water table by capillary action (similar to water travelling up paper towel). H. DEPTH AND USES OF THE WATER TABLE 1. The DEPTH of the water table depends on the rainfall, season, slope of ground, thickness of the soil, climate and time between rainfalls. 2. In swamps, lakes and rivers the WATER TABLE is EXPOSED at the surface. In deserts it may be hundreds of meters down. In fields and farmland it is a few meters down; and in hilly country the water table lies at the surface of the valleys. I. WELLS AND SPRINGS 1. GROUND water is naturally filtered by the ground and is usually clear and drinkable if it hasn't been polluted by human or animal wastes or poisonous materials. 2. The water table is the level of the water in the ground. When a hole is dug into the ground BENEATH the water table, a well is formed. If the water table is above the surface of the ground (as on a hillside) you may have a STREAM. 3. When a permeable layer dips underground between layers of impermeable rock, a "sandwich" is formed called an ARTESIAN layer. The top impermeable layer is called an aquiclude layer. The permeable layer (sandstone or gravel) is an AQUIFER. GRAVITY usually pulls the water into the permeable layer. J. ARTESIAN WELLS 1. ARTESIAN WELLS are formed when wells are dug into the aquifers and the pressure may cause the water to sprout into the air. These wells may be a great distance from the water sources and generally the farther away, the deeper the well. 2. When artesian formations are broken naturally by cracks in the cap rock (FISSURES) the SPRINGS formed are called artesian springs, (i.e. oasis)

4 4 Diagram of an Artesian Well Diagram showing the development of an artesian well. When an acquifer is contained between two impermeable rock layers and part of the acquifer is exposed higher than the well, water will flow from the well due to the pressure of the water that is higher than the well K. CONSERVATION In some areas the GROUND WATER is used too much (for irrigation) and the water table goes down. If it can't be replaced naturally by rain, snow, etc., water should be added by returning used water to the ground. Severe aquifer withdrawal is occurring in the USA. L. GROUND WATER 1. At a depth of 20 m., the temperature remains the same (5-15 C) throughout the year. This usually makes the water from wells cool or cold (even during SUMMER). 2. In the North, the water may be frozen in the PERMAFROST and there are no wells or springs. 3. Below 20 m, heat from Earth's interior raises the temperature about 1 C for every 40m. Water from great depths may be warm or hot. Being close to a volcano can also cause the water to be warm or hot. If hot springs emerge through sticky colored clay, it is called a PAINT POT or MUD VOLCANO. 4. Boiling hot springs that erupt because of some constriction are called GEYSERS. 5. FUMAROLES are holes or fissures in the ground from which steam and hot gases escape (generally around volcanoes). 6. Rainwater is pure due to natural DISTILLATION. Ground water absorbs or dissolves part of what it passes through. Hard water contains dissolved minerals, usually calcium. 7. A mineral spring contains so much dissolved minerals that it can't be used for drinking or washing purposes. It is caused by: a) passage through very SOLUBLE rock b) containing high percentages of ACID-forming gases c) being very HOT.

5 M. CAVERNS AND MINERAL DEPOSITS 1. Limestone is not a porous rock. However, it is frequently split by fissures that run both horizontally and vertically.

5 5 M. CAVERNS AND MINERAL DEPOSITS 1. Limestone is not a porous rock. However, it is frequently split by fissures that run both horizontally and vertically. Groundwater, containing carbonic acid, runs through the cracks and fissures in limestone. The carbonic acid slowly dissolves the limestone and carries it away in solution. After thousands of years fissures grow creating underground tunnels, and large circular openings called SINKHOLES or SINKS. The tunnels are called CAVERNS or CAVES. 2. KARST TOPOGRAPHY refers to areas characterized by sinks, sinkholes, ponds, lost lakes, and underground drainage. N. MINERAL DEPOSITS BY GROUNDWATER 1. The minerals dissolved in groundwater are deposited in a variety of ways. Groundwater drips from rood, slowly deposits calcite in form of icicles hanging from roof, called STALACTITES. (stalactites hold TITE to the ceiling) On the floor below the stalactites blunt round masses called STALAGMITES are formed. (stalagmites MITE rise from the floor) When stalactites and stalagmites meet, COLUMNS or pillars are formed. Diagram of Dripstones 2. These are examples of dripstone - calcite deposits. Dripstone can be formed when a cave is ABOVE the water table, where water can evaporate. Calcite deposits around mineral springs are called travertine. Around the openings of geysers, GEYSERITE is deposited. It is SILICA dissolved from hot igneous rock. 3. Hot groundwater often deposits minerals such as gold, quartz, silver, etc. in cracks and fissures. The most important groundwater deposit is the CEMENT that binds sand grains and pebbles of sedimentary deposits to form sedimentary rock 4. Check out the Virtual Cave web site ( for spectacular photos and descriptions of calcite/carbonate speleothems (dripstones).

label the following: the sun, transpiration, evaporation,

6 6 The Water Cycle What is missing from the diagram below? The SUN Make a reasonable sketch of the diagram above and label the following: the sun, transpiration, evaporation, condensation, precipitation, run-off, groundwater, ocean

7 7 The Water Table Identify the parts of the water table on the following diagram.

What is a water table? What is an aquifer? What is the difference between a spring and a well?

CHAPTER 11 3 Water Underground SECTION The Flow of Fresh Water BEFORE YOU READ After you read this section, you should be able to answer these questions: What is a water table? What is an aquifer? What