Presentation on theme: "Chapter 16. Groundwater Water beneath Earth’s surface Aquifer Body of rock or sediment that stores groundwater Allows flow of groundwater."— Presentation transcript:
Groundwater Water beneath Earth’s surface Aquifer Body of rock or sediment that stores groundwater Allows flow of groundwater
Aquifers Need porosity and permeability Porosity 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 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 37 o C Travertine – mineral deposits from cooled hot springs Mud pots - muddy hot springs clay Paint pots – brightly colored clay
More Mud Pots
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).
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 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.
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
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