Groundwater Chapter 16

Groundwater Aquifer Water beneath Earth’s surface Body of rock or sediment that stores groundwater Allows flow of groundwater

Aquifers Need porosity and permeability Porosity Permeability Percentage of aquifer total volume that is open spaces Permeability Connectivity of pores Allows water to flow through the rock

Aquifer Zones Zone of Saturation Zone of Aeration Pore space completely filled with water Water table – upper surface of this zone Zone of Aeration Lies between water table & Earth’s surface

Water Table Depth Depends on Surface topography (contours usually match local topography) Permeability of aquifer Rainfall amount Rate of human use of water

Groundwater Replenishment May replenish slower than it is used Recharge zones Area where water enters an aquifer Sometimes labeled Near oceans, salt water can flow into an aquifer if too much pumped

Saltwater Can Infiltrate Fresh Water

Wells & Springs Wells Hole dug to the water table to get water Pumping water forms cone of depression Well might run dry

Wells & Springs Springs Natural flow of groundwater to Earth’s surface where the ground dips below the water table Usually found in rugged terrain Can dry up as water table changes

Artesian Formation Sloping layer of permeable rock sandwiched between 2 layers of impermeable rock Caprock – impermeable rock layers Can form artesian well Cone of depression: pumping water from the well lowers the water table around it

Artesian Wells Well through which water flows freely to the Earth’s surface (in normal wells, it has to be pumped) Artesian formation creates pressure to force water out of the ground If caprock cracks, can get an artesian spring or well

Artesian Well vs. Aquifer In a normal aquifer, rock layers are horizontal and lack a cap. In an artesian formation, the permeable rock layer slopes and is covered by an impermeable layer called caprock.

Hot Springs Groundwater passes near magma ands heats up to above 37oC Travertine – mineral deposits from cooled hot springs Mud pots - muddy hot springs clay Paint pots – brightly colored clay

Hot Spring

Deposits

Mud Pots

More Mud Pots

Paint Pot

Geysers Hot springs that periodically erupt from surface pools or through small vents Steam builds up underground and eventually erupts through the vent when the pressure builds up If there is no steam build up underground, there is no eruption (and therefore, no geyser).

Geysers

Weathering by Groundwater Groundwater passes through soil and other organic minerals and forms carbonic acid Groundwater dissolves and breaks down minerals in the rock

Caverns A large cave Stalactites Stalagmite Column Calcite deposited on cave ceiling Stalagmite Calcite deposited on cave floor Column Stalagmite meets stalagtite How caverns form: groundwater flows through cracks & carbonic acid dissolves limestone and makes cracks bigger. This eventually makes a cavern.

Stalactite Stalagmite

Sinkholes Circular depression that forms at the surface when rock dissolves , when sediment is removed, or when caves or mines collapse Subsidence sinkhole depression in ground Collapse sinkhole open hole in the ground

Florida River Runs Into Sinkhole

Sinkhole

Sinkhole

Sinkhole

Natural Bridges Uncollapsed rock between 2 adjoining sinkholes or when two sides of a cavern collapse

Karst Topography Type of topography characterized by sinkholes, caverns, and underground drainage Forms on LIMESTONE and other soluble rock

Karst Topography