Earth's Climate, Geology, and Life: Key Concepts for Study

Presence of liquid water

Liquid water allows carbon-based molecules to form and react, making life possible.

Moderate temperatures allow stable carbon compounds

Earth's temperature range keeps carbon molecules stable and able to form complex structures.

Carbon dioxide

CO₂ traps heat in the atmosphere, helping regulate Earth's surface temperature.

Atmosphere regulates global climate

By trapping heat and distributing energy around the planet.

Weather vs Climate

Weather is daily conditions; climate is long-term patterns.

Local climate

Refers to a small region.

Global climate

Refers to overall climate patterns of Earth.

Equator temperature pattern

The equator is the warmest region due to receiving the most direct sunlight year-round.

Rainiest regions on Earth

Typically found at the equator where warm rising air produces frequent rain and cloud formation.

Oceans regulate climate

By storing and transporting heat.

Milder climates in coastal areas

Oceans heat and cool more slowly than land.

Main cause of seasons on Earth

Earth's tilted axis.

Northern Hemisphere during summer

When the Northern Hemisphere is tilted toward the Sun, it experiences summer.

Solar radiation that reaches Earth

Insolation.

Fate of solar radiation at Earth's surface

It is absorbed, then re-radiated as heat.

Factor increasing global temperatures

Increased greenhouse gases from human activity.

Natural factor causing long-term cooling

Extensive volcanic eruptions releasing ash.

Definition of climate change

Long-term changes in temperature and climate patterns.

Current climate change description

It includes both natural variations and human-driven warming.

Major consequence of global warming

Increased frequency of extreme weather events.

Reason for rising sea levels

Ocean water expands when warmed.

Melting ice

Melting land ice adds water to the ocean, increasing sea level.

Heavy snowfall accumulation

Glaciers grow when snow accumulation exceeds melting.

Melting exceeds snowfall

When ablation surpasses accumulation, the glacier loses mass.

Moraines

Moraines are ridges of debris left by glaciers.

Drumlins

Rounded hills formed by glacial movement.

Alpine glaciers

Alpine glaciers form in mountainous regions.

Ice sheet features

Ice sheets once covered much of the northern US, leaving large-scale features.

Climate proxy

Ice cores contain trapped air bubbles that record past climate conditions.

Tree rings

Ring width reflects annual temperature and precipitation.

Sea level rise

Melting land ice adds water to oceans, raising sea levels.

Ice sheets store water

Water trapped in glaciers lowers global sea levels.

Principle of superposition

Younger layers are deposited on top of older layers.

Fossils in rocks

Used to interpret past environments and relative age.

Angular unconformity

Tilted older layers below horizontal younger layers.

Disconformity

Occurs when sedimentary layers are missing due to erosion.

Parent isotope

The original isotope that decays over time into the daughter isotope.

Half-life

The time for half of the parent isotope to decay.

Numerical dating

Using isotopes to calculate the age of rocks.

Radiometric dating

Best performed on igneous rocks that lock in isotopes when they crystallize.

Isotopes unsuitable for old rocks

Isotopes with half-lives that are too short to date very old rocks.

Suitable isotopes for dating old rocks

Uranium-238 and Potassium-40, which have long half-lives.

Igneous intrusions

Provide maximum or minimum ages for sedimentary layers.

Sedimentary layers

Can be dated using igneous layers that bracket their age.

Radioactive decay

The process by which a parent isotope decays into a daughter isotope.

Erosion

The process that can lead to disconformities by removing sedimentary layers.

Volcanic intrusion

Occurs when volcanic rocks cut through sedimentary layers.

Tilted layers

Indicate past geological deformation and erosion.

Fossil preservation

Not a characteristic of disconformities.

Decay time

Total time taken for isotopes to decay is not the same as half-life.

Dating method

Igneous rocks are preferred for radiometric dating due to their crystallization process.

Gap in sedimentary record

Indicated by disconformities.

Geological history reconstruction

Fossils help in understanding when and where organisms lived.

Sedimentary rock dating

Less effective than igneous rock dating due to lack of isotopes.

Numerical ages calculation

Enabled by understanding half-lives of isotopes.

Volcanic ash layers

They can be radiometrically dated to constrain sediment age.

Formation of the atmosphere

The atmosphere formed early from volcanic outgassing before oceans and life.

Main source of Earth's early atmosphere

Volcanic outgassing.

Correlating rock layers

Geologists can correlate rock layers between distant regions primarily using fossil content and rock type.

Most useful for correlating sedimentary rocks globally

Index fossils.

Correct order of the three eons

Hadean → Archean → Proterozoic.

Paleozoic Era

Part of the Phanerozoic Eon.

Estimated age of Earth

4.54 billion years.

Evidence that helped determine Earth's age

Radiometric dating of meteorites.

Start of the Phanerozoic Eon

Cambrian Explosion.

Changes in life over the last 542 million years

Older species went extinct, new species evolved.

Youngest rocks in a geologic cross section

At the top.

Fault cutting through layers

Fault is younger than the layers it cuts.