Groundwater & Karst Topography

Question 1

Hydrologic Cycle

Answer 1

1) series of storage areas connected by transfer processes + closed/circular system
2) water can cycle through in hours or millions years
3) 99% Earth’s water in storage = oceans, lakes, rivers, ice, aquifers
4) only 2.8% freshwater AND 75% of that water is in glaciers

Question 2

Describe evaporation precipitation balance

Answer 2

1) over the course of years it does balance + cancel each other out
2) tends to be more evaporation compared to precip over ocean, opposite true for continents

Question 3

Residence times

Answer 3

amount of time water spends in a certain substance/medium
- may stay stored in ocean or lake for thousands of years

Question 4

groundwater

Answer 4

1) underground water in subsurface zone where pore spaces completely filled with water (zone of saturation)
2) more than 50% of world’s groundwater within .5 miles underground

Question 5

source of groundwater

Answer 5

majority of groundwater comes as precipitation from above that percolated into soil or seeped downward from lakes

Question 6

Porosity

Answer 6

1) quantity of water that can be held in subsurface material
2) more porous = more open space/cracks = more water stored

Question 7

permeability

Answer 7

1) ability for water to move through soil
2) means the holes/cracks connected

Question 8

Rate at which water moves through rocks depends on

Answer 8

1) permeability
2) porosity
ex = clay has many small interstices that give it high porosity BUT the interstices bind so strongly to water that water cannot move through it

Question 9

aquifers

Answer 9

1) PERMEABLE ROCK where water is stored in sediment underground
2) 3 layers = zone of aeration, zone of saturation, waterless zone

Question 10

aquicludes

Answer 10

1) impermeable materials composed of components like clay which hinder water movement
2) ex = clay + bedrock

Question 11

3 hydrologic zones for groundwater

Answer 11

1) zone of aeration
2) zone of saturation
3) waterless zone

Question 12

Zone of aeration

Answer 12

1) mixture of solids, water, air
2) depth varies
3) interstices filled with water + air
4) water that isn’t held by molecular attraction seeps down

Question 13

zone of saturation

Answer 13

1) pores fully saturated with water
2) water table = top of saturated zone
3) watertable bends to surface above + when it intersects with land –> forms spring
4) humid regions = high water table

Question 14

Cone of depression

Answer 14

1) well filled with water up to water table
2) if water is taken out faster than flows into saturated rock –> creates a “cone of depression” where no water

Question 15

Types of aquifers

Answer 15

1) unconfined (able to enter from any location)
2) confined (only able to fill from one location)

Question 16

How do lakes relate to watertables

Answer 16

Lakes usually depressions that go deep enough into water table

Question 17

confined aquifers

Answer 17

1) when aquifer is confined by acquicludes above + below
2) tends to have a sloping/dipping layer where it absorbs infiltrating water

Question 18

artesian wells

Answer 18

1) when you drill a well into a confined aquifer –> pressure forces water to rise
2) if water rises up to surface = called a artesian well
3) if water only partially rises upward = subartesian

Question 19

piezometric surface

Answer 19

elevation to which water in artesian well rises

Question 20

Groundwater pollution

Answer 20

1) if pollution seeps into aquifer = may remain indefinitely

Question 21

waterless zone

Answer 21

low limit of zone of saturation lacks pore spaces –> has no water

Question 22

Groundwater mining problems

Answer 22

1) groundwater accumulates very slowly (.5 cm/year) but humans tap water very quickly (75 cm/year)
2) can cause subsidence (sinking of land)

Question 23

Fossil water

Answer 23

1) groundwater considered nonrenewable resource

Question 24

Dissolution

Answer 24

removal of bedrock through chemical weathering + action of water

Question 25

Role of Bedrock in dissolution

Answer 25

Joints + bedding planes allow groundwater to penetrate rock easily –> resulting in more water which can dissolve calcium bicarb

Question 26

Precipitation

Answer 26

1) Hot springs + geysers provide accumulation of precipitated materials
2) Hot water (heated by magma) dissolves more

Question 27

Caverns

Answer 27

open areas created by dissolution along joints + bedding planes

Question 28

Speleothems

Answer 28

formed by precipitation bc water leaves behind compounds (carbon dioxide + calcite)
stalactite = on roof, stalagmite = on bottom

Question 29

Cave formation steps

Answer 29

1) cavern formed by dissolution when percolating water dissolves carbonate bedrock
2) decoration stage = formation of spleothems (precip occurs when you remove h20 or co2 from calcium limestone water slurry)

Question 30

Where does cave formation occur

Answer 30

1) mainly in tropical climates because it has water + good drainage in soils

Question 31

Karst landforms

Answer 31

1) typical landforms in karst regions are sinkholes, disrupted surface drainage, underground drainage networks
2) form where there is massive LIMESTONE bedrock water air

Question 32

Denudation cycle of Karst

Answer 32

1) weathering = chemical + carbonation
2) no mass wasting (since it’s not going downward anywhere)
3) erosion = (pickup, transport, deposition) precipitation
SO ITS BASICALLY
1) dissolution caused by carbonic acid (formed by water + co2)
2) precipitation (carbonic acid breaks down carbonate rocks like limestone) to form calcium bicarb that dissolves in water

Question 33

Sinkholes

Answer 33

1) rounded depressions formed by dissolution of carbonate rocks (shallow limestone)
2) collapse sinkhole = result of sediment over limestone + limestone breaks away + causes sudden collapse

Question 34

Effect of sinkholes on drainage

Answer 34

1) channel surface runoff into groundwater circulation
2) creates uvala = chain of intersecting sinkholes
3) disappearing streams = surface runoff disappears into sinkhole/crack

Question 35

Tower karst

Answer 35

residual karst features –> steep hills caused by intense rainfall that contributes to dissolution around base of hills

Question 36

Mogotes + haystack hills

Answer 36

limestone dissolved away (late stage karst) + leaves behind massive haystack hills

Question 37

Hydrothermal activity

Answer 37

where hot water comes to surface through natural openings

Question 38

Hot springs

Answer 38

1) hot water at earth’s surface = indicates that water has come into contact with heated rocks + magma
2) sloping land = forms terraces
3) flat land = forms deposits

Question 39

Geysers

Answer 39

1) special intermittent hot spring
2) water accumulates in deep reservoirs, heats to 200 C without boiling (due to high pressure above it) and suddenly surges upward creating an eruption

Question 40

Fumarole

Answer 40

1) surface crack directly connected to deep-seated heat source
2) when water drains into it, forms a cloud of steam
3) essentially hot spring without water
4) can become a mudpot