SACE Stage 2 Earth and Environmental Science flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Earth's four spheres

Geosphere, atmosphere, hydrosphere and biosphere. Each stores matter and energy and exchanges them with the others, so a change in one sphere typically produces a response in another.

Closed versus open system

A closed system exchanges energy but not matter with its surroundings; an open system exchanges both. Earth overall is closed for matter but open for solar and internal energy.

Albedo

The fraction of incident solar radiation reflected by a surface, expressed 0 to 1. Snow and ice have high albedo, oceans and dark forest low albedo, controlling how much energy is absorbed.

Ice-albedo feedback

A positive feedback in which warming melts reflective ice, exposing darker land or ocean, which absorbs more solar energy and causes further warming and melting.

Residence time

The average time a substance remains in a reservoir, calculated as reservoir size divided by the rate of input or output. Long residence times mean slow responses to change.

Positive feedback loop

A feedback that amplifies the original change, moving the system further from its starting state. Permafrost thaw releasing methane, which causes more warming, is an example.

Negative feedback loop

A feedback that opposes the original change and stabilises the system. Increased cloud cover reflecting sunlight as oceans warm is a commonly cited example.

Convergent plate boundary

A boundary where plates move toward each other. Oceanic crust subducts beneath less dense plates, generating volcanoes, deep trenches and earthquakes; continental collision builds mountain belts.

Rock cycle

The set of processes converting rock among igneous, sedimentary and metamorphic types through melting, crystallisation, weathering, erosion, deposition, compaction, cementation, heat and pressure.

Reserve versus resource

A reserve is the identified, currently economic and legally extractable portion of a resource. A resource also includes undiscovered and currently uneconomic material.

Ore grade and cut-off grade

Ore grade is the concentration of a target element in rock. Cut-off grade is the minimum concentration that can be mined economically, rising as energy and processing costs rise.

Acid mine drainage

Acidic, metal-rich water formed when sulfide minerals in mine waste oxidise on exposure to air and water. It can contaminate streams and groundwater long after mining ends.

Fossil fuel formation

Buried organic matter, heated and compressed over millions of years, converts to coal from land plants and to oil and gas from marine plankton, which then migrate into porous reservoir rock.

Aquifer and confining layer

An aquifer is permeable rock or sediment that stores and transmits usable groundwater. A confining layer is low-permeability material that restricts water movement into or out of it.

Groundwater recharge

The rate at which water infiltrates and refills an aquifer. Extraction exceeding recharge lowers the water table, dries springs and can cause land subsidence.

Soil salinisation

Accumulation of soluble salts in soil, often from irrigation with saline water and high evaporation. It raises osmotic stress and reduces crop yields, degrading agricultural land.

Renewable resource

A natural resource replenished by natural processes at a rate comparable to or faster than human use, such as solar energy, wind, and sustainably harvested timber.

Energy density of fuels

Energy released per unit mass of fuel. It is very high for uranium, high for oil and gas, and lower for coal, affecting transport, storage and waste volumes per unit energy.

Greenhouse effect

Atmospheric gases absorb and re-emit outgoing longwave radiation, warming the surface. Water vapour, carbon dioxide, methane and nitrous oxide are the main contributors.

Radiative forcing

The change in net energy flux at the top of the atmosphere, measured in watts per square metre. Positive values warm the climate system; negative values cool it.

Keeling curve

The continuous record of atmospheric carbon dioxide measured at Mauna Loa since 1958, showing a long-term rise plus an annual sawtooth from Northern Hemisphere growing seasons.

Weather versus climate

Weather is the short-term state of the atmosphere at a place and time. Climate is the statistical distribution of weather over decades, conventionally a 30-year period.

Climate proxy data

Indirect evidence preserving past climate signals, including ice-core isotopes and trapped air, tree rings, corals, ocean sediments, pollen and historical records.

Climate projection

A modelled future climate conditional on a stated scenario of emissions or forcing. It is not a single forecast, and its uncertainty range widens with time and scenario spread.

Ocean acidification

Uptake of atmospheric carbon dioxide by seawater forms carbonic acid, lowering pH and reducing carbonate availability for shell-forming organisms such as corals and molluscs.

Mitigation versus adaptation

Mitigation reduces greenhouse gas emissions or enhances sinks to limit forcing. Adaptation adjusts systems to reduce vulnerability to impacts already locked in.

Attribution of warming

Linking observed change to a cause using pattern evidence. Combined tropospheric warming and stratospheric cooling matches greenhouse forcing, unlike solar or volcanic forcing.

Independent and dependent variables

The independent variable is deliberately changed by the investigator. The dependent variable is measured as the response, while all other conditions are held constant.

Validity and reliability

Validity is whether a method measures the intended quantity. Reliability is whether repeated measurements under the same conditions give consistent results.

Accuracy versus precision

Accuracy is closeness to the true value. Precision is closeness of repeated measurements to each other, so results can be precise yet consistently offset by a systematic error.

Random versus systematic error

Random errors scatter results unpredictably about a mean and are reduced by averaging repeats. Systematic errors shift all results in one direction and are not reduced by averaging.

Correlation and causation

Correlation means two variables vary together. Claiming causation requires a plausible mechanism, the cause preceding the effect, and control of confounding variables.

Extrapolation risk

Extending a trend beyond the range of measured data. It is unreliable because the relationship may change outside the observed range and uncertainty grows rapidly.