HS Earth Science practice questions and exam guide

A galaxy is best described as:

1. Empty space between stars
2. A single planet
3. The same thing as a solar system
4. A gravitationally bound system of stars, gas, dust, and dark matter — often containing hundreds of billions of stars

Answer: D — A gravitationally bound system of stars, gas, dust, and dark matter — often containing hundreds of billions of stars

D) Astronomy textbook definition. A/B/C) Each is wrong scale.

Earth's magnetic field:

1. Generated by motion of liquid iron-nickel in the outer core (geodynamo) — protects Earth from solar wind (creates auroras at poles); has reversed polarity many times geologically
2. Comes from the crust
3. Generated by the Sun
4. Doesn't exist

Answer: A — Generated by motion of liquid iron-nickel in the outer core (geodynamo) — protects Earth from solar wind (creates auroras at poles); has reversed polarity many times geologically

A) Standard explanation. B/C/D) Each is incorrect.

River system features:

1. Headwaters (source), tributaries (smaller rivers joining), main channel, floodplain, meanders (curves), oxbow lakes, deltas (at mouth); transport water + sediment from watershed to ocean
2. Only delta
3. None exist
4. Random

Answer: A — Headwaters (source), tributaries (smaller rivers joining), main channel, floodplain, meanders (curves), oxbow lakes, deltas (at mouth); transport water + sediment from watershed to ocean

A) Standard. B/C/D) Each is incomplete.

Sustainable practices to reduce impact:

1. Renewable energy use, energy efficiency, sustainable transportation, plant-rich diet (less meat), reducing food waste, sustainable purchasing, supporting conservation policies, civic engagement, education — individual and systemic changes both matter
2. Have no effect
3. Only one action
4. Random

Answer: A — Renewable energy use, energy efficiency, sustainable transportation, plant-rich diet (less meat), reducing food waste, sustainable purchasing, supporting conservation policies, civic engagement, education — individual and systemic changes both matter

A) Standard. B/C/D) Each is incomplete.

Most of Earth's atmosphere is composed of:

1. Oxygen
2. Carbon dioxide
3. Nitrogen
4. Argon

Answer: C — Nitrogen

The atmosphere is about 78% nitrogen, 21% oxygen, with trace argon, CO₂, and other gases.

Mass extinctions in Earth's history:

1. Never happened
2. Just dinosaurs
3. Five major mass extinction events: Ordovician, Devonian, Permian (largest, ~96% marine species), Triassic, Cretaceous-Paleogene (KPg, killed dinosaurs ~66 mya)
4. Continual
5. None known

Answer: C — Five major mass extinction events: Ordovician, Devonian, Permian (largest, ~96% marine species), Triassic, Cretaceous-Paleogene (KPg, killed dinosaurs ~66 mya)

Big Five mass extinctions: end-Ordovician, late Devonian, end-Permian (Great Dying, ~252 mya), end-Triassic, end-Cretaceous (KPg, asteroid + Deccan Traps, dinosaurs out). Many scientists argue current human-caused 'Sixth Extinction' underway.

Index fossils are useful because they:

1. Have no useful properties
2. Lived in only one location for a billion years
3. Are always vertebrates
4. Lived for a short geologic time and were geographically widespread

Answer: D — Lived for a short geologic time and were geographically widespread

D) Short range + wide distribution = good for correlation. A/B/C) Wrong.

Earth's atmosphere layers, low to high:

1. Random order
2. Just ionosphere
3. Just troposphere
4. Troposphere (weather), Stratosphere (ozone layer), Mesosphere (meteors burn up), Thermosphere (auroras, ISS), Exosphere
5. Inside out

Answer: D — Troposphere (weather), Stratosphere (ozone layer), Mesosphere (meteors burn up), Thermosphere (auroras, ISS), Exosphere

Atmosphere layers by altitude: Troposphere (0-12km, where weather happens), Stratosphere (12-50km, ozone), Mesosphere (50-85km, meteors burn), Thermosphere (85-600km, aurora, ISS), Exosphere (transitions to space). Density decreases with altitude.

Which sequence shows part of the rock cycle?

1. Magma → diamond → gold
2. Mineral → atom → rock
3. Soil → sand → ocean → mineral only
4. Igneous → weathering/erosion → sediment → sedimentary rock

Answer: D — Igneous → weathering/erosion → sediment → sedimentary rock

D) Standard pathway. A/B/C) Not valid transformations in the cycle.

Carbon cycle includes:

1. Just plants
2. Just animals
3. Movement of carbon through atmosphere, oceans (largest reservoir, dissolved), biosphere (photosynthesis, respiration), and lithosphere (fossil fuels, carbonate rocks)
4. Just oceans
5. Soil only

Answer: C — Movement of carbon through atmosphere, oceans (largest reservoir, dissolved), biosphere (photosynthesis, respiration), and lithosphere (fossil fuels, carbonate rocks)

Carbon cycle: photosynthesis takes CO₂ from atmosphere into biomass; respiration/decomposition returns to atmosphere; ocean exchange; long-term storage as fossil fuels and carbonate rocks (limestone). Human disruption: rapid release from fossil fuels.

Volcanoes typically form near:

1. Stable plate interiors
2. Just deserts
3. Random locations
4. Plate boundaries (subduction zones — Ring of Fire) and hotspots (e.g., Hawaii)
5. Just poles

Answer: D — Plate boundaries (subduction zones — Ring of Fire) and hotspots (e.g., Hawaii)

Volcano formation: ~75% near subduction zones (Ring of Fire around Pacific). Mid-ocean ridges (spreading). Hotspots (mantle plumes — Hawaii, Yellowstone). Continental rifts. Types: shield (broad, basaltic), composite/strato (steep, andesitic), cinder cone.

Which sequence shows the geologic time hierarchy from longest to shortest?

1. Era → Eon → Epoch → Period
2. Period → Era → Eon → Epoch
3. Epoch → Period → Era → Eon
4. Eon → Era → Period → Epoch

Answer: D — Eon → Era → Period → Epoch

D) Standard nested order. A/B/C) Wrong ordering.

Layers of Earth (inside out)?

Inner core (solid iron), outer core (liquid iron), mantle (mostly solid), crust.

Where is most of Earth's water?

Oceans (~97%). Then ice caps, groundwater, surface water (small fractions).

Half-life?

Time for half of radioactive material to decay. Each isotope has fixed half-life.

Global warming evidence?

Rising temperatures, melting glaciers/ice sheets, sea level rise, ocean acidification, shifting ecosystems.

Topographic map?

Shows elevation via contour lines. Closer lines = steeper slope.

Conservation strategies?

Recycling, renewable energy, sustainable farming, protected areas, habitat restoration.