Oceanography Chapter 4 & 5

What is a mass extinction event? (ch.4)

A widespread and rapid decrease in biodiversity on Earth, where many species go extinct in a relatively short geologic time.

What happened at the end of the Permian period (~252 mya)? (ch.4)

The largest mass extinction in Earth's history; marked the end of the Paleozoic Era.

What happened at the end of the Cretaceous period (~66 mya)? (ch.4)

Mass extinction that ended the Mesozoic Era, including the extinction of dinosaurs.

What are two main hypotheses for mass extinction events? (ch.4)

Extraterrestrial impacts and intense volcanic eruptions.

What evidence supports the extraterrestrial impact hypothesis for the end-Cretaceous extinction? (ch.4)

Iridium-rich layer, impact crater (e.g. Chicxulub crater), shocked quartz, and tektites.

What is relative geologic time? (ch.4)

Relative time tells the order of events, not exact dates.
Key principles:

• Original horizontality: Layers are originally flat.

• Superposition: Older rocks are below younger ones.

• Cross-cutting relationships: Cuts (faults, intrusions) are younger than what they cut.

• Faunal succession: Fossils appear in a predictable vertical order.

What are unconformities in geology? (ch.4)

Unconformities represent gaps in the rock record due to erosion or non-deposition.

Types:

• Disconformity: Layers are parallel, but time gap exists.

• Angular unconformity: Older tilted layers with flat layers above.

• Nonconformity: Sedimentary layers over igneous or metamorphic rock.

What is correlation, and how are fossils used in it? (ch.4)

Correlation connects rock layers of the same age across locations.

• Index fossils help correlate layers: they are widespread, short-lived, and easily recognized.

• Key beds, like the iridium layer at the KT boundary, are also useful markers.

What is absolute geologic time/dating, and how is it measured? (ch.4)

Absolute dating gives actual ages using radioactive isotopes.

• Half-life: Time for half the parent isotope to decay into daughter isotope.

• Radiometric dating measures the ratio of parent to daughter isotopes.

What is carbon-14 dating, and when is it used? (ch.4)

• C-14 has a half-life of 5,730 years and is used for dating once-living things up to ~50,000 years old.

• C-14 decays into N-14; the C-14 to C-12 ratio reveals age.

How old is the Earth, and what is the Precambrian? (ch.4)

• Earth is about 4.6 billion years old.

• The Precambrian is the time before the Phanerozoic, covering most of Earth’s history and early life forms.

What are the three eras of the Phanerozoic Eon? (ch.4)

Paleozoic, Mesozoic, and Cenozoic.

When did the Paleozoic Era begin, and what life was dominant? (ch.4)

~541 million years ago; marine invertebrates and early fish.

When did the Mesozoic Era begin, and what life was dominant? (ch.4)

~252 million years ago; dinosaurs and early birds.

When did the Cenozoic Era begin, and what life was dominant? (ch.4)

~66 million years ago; mammals and flowering plants.

(ch.4) A rock contains 12.5% of a parent isotope and 87.5 of a daughter isotope. If the half-life of this isotope is 350 million years old, the rock is —- years old.

1.05 billion

What are mineral resources and ores? (ch.5)

Mineral resources are naturally occurring materials used by humans.
Ores are rocks that contain enough valuable metal or mineral to be mined profitably.

What are examples of non-metallic mineral resources? (ch.5)

Non-metallic resources include halite (salt), gypsum, borax, and sodium sulfate. These are often used in construction and industry.

How do magmatic processes form ore deposits? (ch.5)

As magma cools, crystal settling causes heavy minerals to sink and accumulate in layers, forming ore deposits.

What are hydrothermal processes and how do they form ores? (ch.5)

Hot water (often from magma or deep groundwater) dissolves minerals and deposits them in cracks or pores in rock as it cools.
This occurs in places like cooling granitic magma zones and mid-ocean ridges (black smokers).

What are sedimentary ore deposits? (ch.5)

• Placer deposits: Form in riverbeds where heavy minerals like gold settle out of water.

• Precipitate deposits: Form from evaporating water, leaving behind minerals like halite or gypsum.

What are fossil fuels and what do they have in common? (ch.5)

Coal, petroleum (oil), and natural gas are fossil fuels formed from ancient organic matter.
They are all nonrenewable, unrecyclable, and release CO₂ when burned.

How does petroleum (oil) form and accumulate underground? (ch.5)

Oil forms in source rock, then migrates upward into porous reservoir rock, where it's trapped beneath a cap rock.
Traps include: folds, faults, unconformities, and salt domes.

What is natural gas and where is it found? (ch.5)

Natural gas forms similarly to oil and is often found above oil in the same traps. It is a cleaner-burning fossil fuel.

What are examples of renewable energy resources? (ch.5)

• Solar: thermal (heating) and photovoltaic (electricity)

• Wind: wind turbines

• Water: hydroelectric, wave, and tidal power

• Geothermal: uses Earth’s internal heat

How does a nuclear fission reactor work, and what are its disadvantages? (ch.5)

Fission splits atomic nuclei (e.g., uranium) to release heat, generating electricity.
Disadvantages: radioactive waste and risk of serious accidents.

How is energy used in the U.S., and how can it be conserved? (ch.5)

• Buildings (39%): Use efficient lighting, heating, insulation

• Industry (33%): More efficient motors (especially electric)

• Transportation (28%): Efficient vehicles, public transit, carpooling

How can society help conserve energy? (ch.5)

By changing behaviors (e.g., using less energy, choosing efficient options), and investing in cleaner technologies.