unit 16

Scientists believe some water outgassed from rocks and some water-rich carbonaceous chondrite meteorites delivered water later.

Water makes up about 0.02% of the Earth's mass, and only about 2.5-3% of Earth's water is freshwater.

Groundwater is water beneath Earth's surface, not water on the ground like rivers or lakes. Approximately 30% of Earth's freshwater is groundwater.

An aquifer is a body of rock or sediment in which large amounts of water can flow and be stored. Aquifers are important sources of drinking water and irrigation water.

Porosity is the percentage of the total volume of a rock or sediment that consists of open spaces. Permeability is the ease with which water passes through a porous material.

Porosity depends on particle size, particle shape, and how well-sorted the particles are.

Permeability depends on the connectedness of pores and the size of the pores.

Shale is often relatively impermeable because it is made of fine-grained clay minerals with small, poorly connected pores. Sandstone is typically porous and permeable because it has larger quartz grains and connected pore spaces.

Quicksand is sand whose pores are saturated with water. A person can sink in it, but you are unlikely to drown because humans are not as dense as quicksand.

The water table is the upper surface of the zone of saturation, where pore space is completely filled with water.

A perched water table is a local water table that forms above the main aquifer when an impermeable layer traps water.

The zone of aeration, or vadose zone, lies between the water table and Earth's surface and contains both air and water in its pores. The capillary fringe is the bottom region just above the water table where water is drawn upward from the zone of saturation by capillary action.

Shallow water tables generally match the contours of the surface. If the water table is above the surface, surface water features like rivers and lakes form.

Yes. Groundwater flows downward in response to gravity, and its rate of movement depends on aquifer permeability and the gradient of the water table.

A well is a hole dug below the water table so groundwater can be brought to the surface. A spring is a natural flow of groundwater to Earth's surface where the surface dips below the water table or where a perched water table is exposed.

An artesian well occurs when water in an aquifer is under enough pressure, usually from downhill flow, to force it up the well above the top of the aquifer. It is "flowing" if it rises without pumping.

Both are places where groundwater reaches Earth's surface. A spring has enough volume to flow, while a seep is only a moist or wet place with too little water to flow beyond the area.

A recharge zone is any area where water from the surface can travel through permeable rock to reach an aquifer. Common contamination sources include waste dumps, underground storage tanks for toxic chemicals, fertilizers and pesticides, and leaking sewage systems.

Overdrafting is removing groundwater faster than it can be replaced. It can cause future water shortages and subsidence, where land sinks as pore water pressure is lost.

Hot springs are heated when groundwater passes through rock heated by magma. Heated groundwater can also produce fumaroles and geysers.

Both involve heated groundwater. A fumarole is steam escaping immediately, while a geyser erupts explosively because pressurized water flashes to steam in a narrow vent.

Hot spring water often contains a high concentration of dissolved solids because heated water can hold more dissolved minerals than cold water. It may be alkaline, acidic, or silica-rich.

Hot springs are often brightly coloured because extremophiles live in the mineral-rich water and their pigments contribute vivid colours.

Hard water contains relatively high concentrations of dissolved minerals, especially calcium, magnesium, and iron. It becomes hard as groundwater dissolves minerals from rocks while passing through permeable rock.

We use water softeners because hard water is less desirable, needs more soap to make suds, and can cause mineral buildup that damages fixtures and appliances.

A cavern is a large cave made up of many connecting chambers. It forms when groundwater chemically weathers rock, especially limestone, and dissolves it over time.

Stalactites hang from cave ceilings, and stalagmites build up from cave floors. Other cave formations include straws, flowstone, and drapery.

Stalactites form when calcite from dripping water is deposited on the ceiling. Stalagmites form when the drops fall to the floor and deposit calcite there.

Sinkholes form when the ground subsides or collapses into a cavern. A cenote is a sinkhole that exposes groundwater.

A karst landscape is an area with many caverns and sinkholes. It forms in limestone. The karst conservation area on East Hamilton Mountain is the Eramosa Karst Conservation Area.