Geol 142 Midterm

Where is most of Earth's water located?

Oceans, ice caps, and glaciers (≈99%)

What qualities allow Earth to have all three phases of water?

Temperature and pressure

T/F: ice is more dense than water

False

Temperature of water at max density

4°C

What quality of water allows fish to survive in the winter?

Max density is at 4°C, so it sinks to the bottom—meaning lake water never gets below 4°C

Heat capacity

Heat input needed to raise the temperature of a substance by 1°C

Heat is released when water...

....freezes/condenses

Heat is absorbed when water...

....melts/evaporates

Does land or water heat faster?

Land

Natural causes of climate change

Tectonic activity, changes in Earth's orbit, changes in the Sun's strength

Anthropogenic (human) causes of climate change

Alterations of land surface, addition of greenhouse gases

What is in rainwater?

<10 ppm TDS, dissolved CO2

Chemical weathering

Reaction between oxygenated, acidic (CO2) water & minerals

Effects of chemical weathering

Produces soils, land forms, new minerals, sediments, dissolved substances, & regulate atmospheric CO2

Congruent chemical weathering

Mineral completely dissolves into a solution, leaving a hole in the Earth materials, and puts ions into the solution

Incongruent chemical weathering

Most important near-surface processes; produces new amorphous substances and minerals (clays and iron oxides)

Most important incongruent weathering includes these minerals

Feldspars, amphiboles, pyroxenes, and micas

Why is the ocean salty?

Dissolved ions from rivers gathers and concentrates in the oceans

Basic controls of seawater composition

River water & mid-ocean ridge hydrothermal water mixing; biogenic and chemical precipitation of CaCO3 and SiO2

Groundwater

Mass of water in the ground, occupying pore space and moving downhill as permeability allows

Aquifer

A body of permeable rock or sediment saturated with water, through which groundwater moves

Porosity

Volume of a rock, sediment, or soil that is filled with holes (amount of open space)

Permeability

Capacity for transmitting fluids; how connected the holes are

Unsaturated zone

Groundwater zone in which open spaces in soil are filled mainly air or air and water

Saturated zone

Groundwater zone in which all openings are filled with water

Water/groundwater table

Upper surface of saturated zone; normally slopes toward the nearest stream or lake and follows general topography

Percolation

The movement of groundwater

Recharge area

Water added to the saturated zone

Discharge area

Where water is discharged into streams or bodies of surface water

Groundwater discharge determined by:

Cross-sectional area, permeability, and hydraulic gradient

Aquifer cross-sectional area

How big it is

Hydraulic gradient/head

The slope of the water table

Darcy's Law

Q = (A)(K)(h/l) where Q = flow rate, A = area, K = permeability, h/l = gradient

State that has some of the biggest aquifers in the US

Florida (technically Georgia, Alabama, and South Carolina too but Florida is the only one that's fully in the aquifers)

Where is salty water more common in the Earth?

Deeper

Largest aquifer in the US

Ogallala Aquifer: flow velocity ≈ 30 cm/day; supplies 20% of irrigated land in the US; contains more than 150,000 wells

Concern for the Ogallala Aquifer

Water mining: withdrawal is far greater than recharge

Ogallala region farming

20% of nation's corn, wheat, and cotton production; as well as 20% of cattle

Ogallala Aquifer region with highest rate of decline

Southern; recharge rates low, irrigation demand highest

Groundwater quality determined by these properties:

Mineral particles, dissolved substances, organic matter, industrial contamination, PFAS, nuclear waste

TDS concentration regulation level

>500 ppm

Point source pollution

Identifiable, small-scale source which produces a well-defined plume (ex: leaking storage tank or landfill)

Non-point source pollution

Large-scale, relatively diffuse contamination from many smaller sources (ex: herbicides, pesticides, salt from roads)

Major contaminants organized into:

Trace metals, nutrients, microbes, organic compounds, radioactive waste

Drinking water issues in low and middle income countries

Fecal contamination, accessibility, availability, improved (source with potential for safe water)

Countries (>50% of population) exposed to contaminated drinking water

Oceania, sub-Saharan Africa, southeastern Asia, Latin America, Caribbean

Flint, MI contaminent

Lead

US regulation for lead concentration, and the amount found in Flint, MI in 2015

15 µg/L, >5000 µg/L (ppb)

Biggest source of lead in Flint, MI

Lead pipes / service lines

Arsenic concentration regulation level

10 µg/L (ppb) (but also sometimes 0 µg/L?)

Sources of arsenic pollution

Subsurface sediments and rocks; mining processes and mining waste

Dangers of arsenic

Cancers, skin lesions, hypertension, cardiovascular disease, neurological effects, diabetes, birth problems

Sands without arsenic

Orange, Fe(III) and As(V) ions present

Sands with arsenic

Gray, Fe(II) and As(III) ions present

Source of arsenic in India

Himalayan coal seams & rocks containing sulfides

Vestal lead amounts

Average: 0.4 µg/L; highest: 2.5 µg/L (ppb)

PFAS stands for:

Perfluoroalkyl and polyfluoroalkyl substances; "forever chemicals"

Some sources of PFAS

Teflon, Nylon, shampoo, wall paint, food packaging, heat-resistant non-stick cooking surfaces, firefighting foam, cosmetics, personal care products

Health effects of PFAS

Reproductive effects, developmental effects, some cancers, reduced immune system, interference with hormones, increased cholesterol, risk of obesity

Health effects difficult to specify because:

Thousands of PFAS exist with varying toxicity, but very few studies around them; exposure can change throughout a lifetime; types and uses of PFAS change (which makes it challenging to track)

Percent of US population with detectable PFAS in their blood

>98%

Highest PFAS levels in water is found where?

Near industrial facilities where PFAS are manufactured or processed

PFOS and PFOA concentration regulation

4 ng/L (ppt)

18-80 million Americans exposed to what level of PFOS and PFOA?

≥10 µg/L (ppb)

200 million Americans exposed to what level of PFOS and PFOA?

≥1 µg/L (ppb)

How many Americans are exposed to concerning levels of six concerning PFAS in drinking water?

70-94 million

Type of rock where hydrofracking occurs

Marcellus shale

How much water does each hydrofracking well need?

4 million gallons

One very toxic chemical used in fracking

Ethylene glycol

How could fracking wells contaminate nearby water?

Leaks, cracks, or holes in the wells

Briefly, how does hydraulic fracking work?

High pressure water, sand, and chemicals shot into the wells, splits rocks & creates ways for the gas or oil to escape. Sand keeps the cracks open

What happens to fracking wastewater?

Reused (best option), injected underground (second best), or put into evaporation pond (not good—bad odor, airborne chemicals, plastic liner may not hold)

Environmental effects of fracking

Man-made earthquakes, water contamination, noise pollution

How many active fracking wells in the US?

≈150,000

How many people rely on water within 1 mile of a fracking well?

>9 million

Potential water contamination from fracking

Surface spills, release of improperly treated wastewater, leaks in the well

How many fracking wells reported spills?

1-4% (1500-6000)

How many fracking wells reported a non-administrative violation?

≈20%

Health effects of those living near fracking

Adverse perinatal outcomes, childhood cancers, hospitalizations, asthma, mental health issues, mortality in the elderly

Are private wells subject to federal regulations?

No

How many chemicals are used in fracking wells?

≈1200

Percentage of chemicals in fracking water

0.01-0.05% (100-500 ppm; 100,000,000-500,000,000 ppt)

If these chemicals are carcinogens & have a low tolerance in drinking water, why is fracking allowed to use them?

Special privileges

Percent of fracking sites that had accidents leading to contamination

20%

Climate

Average condition of a region over years or longer

Weather

Condition of the atmosphere at a particular time and place

What effects have humans had on the climate?

Alterations of land surface; greenhouse gases (the important one)

Why do global temperature data start at 1880?

Industrial Revolution

About when did fossil fuel usage skyrocket?

1980

How much has Earth's average temperature increased since 1880?

≈2.0°F (1.1°C)

Briefly, how does the greenhouse effect work?

Infrared radiation from Earth's surface absorbed and re-emitted by gases

Where does CO2 go?

Biosphere (15-20%), oceans (25-30%), and atmosphere (55%)

Current CO2 concentration (Feb 28, 2025)

426.9 ppm

Future climate change will be impacted by:

Population growth, increased emissions, economic growth, technology, increased standard of living, increased use of natural gas

Last glacial maximum

20,000 years ago; CO2 was ≈180 ppm

Number of years between interglacial periods

100,000

Eocene Green River formation

50 million years old; fossils, oil shale, sodium carbonate minerals

What were CO2 levels during the Eocene period?

≈720-1600 ppm

Fossils that prove it was much warmer in the Eocene? (found in Wyoming)

Palm trees and crocodiles (frost-sensitive)

Proof of high levels of CO2 in the Eocene period (Green River, Colorado)

Nahcolite mineral: only forms with extremely high levels of CO2