GEOL MIDTERM Flashcards
What is the definition of Geology/geoscience?
The science that pursues an understanding of the earth and other planets.
What are the 2 main areas of geology? Give a description of each.
- Physical Geology (Examines the materials that make up the planets and tries to understand the processes acting on these materials, as well as what’s formed as a result. It looks at what makes up the earth; what is happening on and beneath the ground.)
- Historical Geology (Examines earth’s history and understanding the origin of earth and its development through time; the history of life on earth. Deals more with the life on earth.) Ex) Looking at fossils.
What are some problems that geology addresses?
Natural hazards, resources, world population and growth, and environmental issues.
What are the 2 different ideas of how the earth is shaped? Give a description of each.
- Catastrophism: Says catastrophes are responsible for the earth’s creation. Believes in sudden processes. (Things like volcanoes shape the landscape)
- Uniformitarianism: Says Geological processes that operate today have also operated in the geologic past. It takes time, it’s not sudden: processes today have happened in the past.
How old is the earth?
Around 4.6 billion years old.
The present is key to the past: Natural processes have been uniform through time. True or false?
True.
Are geologic changes slow or fast?
Very slow. Earth processes take a long time to create or destroy major landscape features.
What is relative dating?
Dates are placed in their proper sequence/order without knowing the exact age in years.
What do Geologists use with relative dating?
With geologic time scale to ‘time’ things, and apply Principles of Superstition and Fossil Succesion.
What is the Geologic Time Scale?
It’s Earth’s calendar; it summarizes Earth’s history. It exists because the Earth involves vast amounts of time, and humans are only a tiny part of it.
What are the different stages of the Geologic Time Scale?
Each eon is divided into an era, nad each era is divided into periods, and each period is divided into epochs.
1. Eons (The largest subdivision of time: Hundreds of thousands of Ma)
2. Eras (65 to hundreds of Ma)
3. Periods (2 to 70 Ma)
4. Epochs (0.011 to 22 Ma)
Why oes the Precambrian section take up 88% of the time scale?
Because it’s harder to specifically ‘time’ those fossils, if any were found.
How much of earth’s history do humans occupy?
0.000001%
What are the 4 different eons?
- Phanerozoic: Visible life, from 542 to 0 Ma.
- Proterozoic: Before life, from 2.5 to 0.452 Ga.
- Archean: Ancient, from 3.8 to 2.5 Ga.
- Hadean: Hell, from 4.6 to 3.8 Ga.
What are the 3 different eras?
- Cenozoic: Recent life. The Era we’re in.
- Mesozoic: Middle life.
- Paleozoic: Ancient life.
What does Ga mean?
Giga annum: Billions of years.
What does Ma mean?
Mega annum: Millions of years.
What does Ka mean?
Kilo annum: Thousands of years.
What 3 major eons is the Precambrian stage divided into?
Hadean, Archean, and Proterozoic.
What 3 major eras is the Phanerozoic eon divided into?
Paleozoic, Mesozoic, and Cenozoic.
What is the goal of science?
To discover patterns in nature and use this knowledge to make predictions or generate an understanding of phenomena.
Why do we look for patterns in science?
Because we assume that nature is consistent and predictable.
What is a hypothesis?
An untested explanation.
What is a theory?
A well-tested and widely accepted view that scientists agree best explains certain observable facts.
How are geological questions investigated?
With deductive reasoning and scientific methodology. Any question or idea in geology must be tested.
What is the scientific method? What are its stages?
It uses observations and experiments to build and refine hypotheses that explain phenomena. Any explanation for a process/phenomenon must be testible.
What are the 4 stages of the scientific method?
- Observation (Use inductive reasoning)
- Build/modify your hypothesis/model.
- Make a prediction (the result you’re expecting).
- Design an accurate test, and then test your prediction.
What does it mean to ‘pass the test’ in stage 4 of the scientific method? What does it mean to fail?
To pass means that you got the expected results, and it can become a theory when repeatedly tested.
To fail means you got unexpected results, so you can modify (go back to step 2) or reject your hypothesis.
The theory of plate tectonics is the worst explanation for how the earth ‘works’. True or false?
False, it’s the best explanation.
How many rigid plates are on earth?
At least 15.
How does plate motion define the 3 types of plate boundaries (It provides a unified mechanism that explains what)?
- The distribution of earthquakes and volcanoes.
- Changes in past positions of continents and ocean basins.
- The origins of mountain belts and seamount chains.
- The origins and ages of ocean basins.
What are plate boundaries? How were they identified?
Places on earth where tectonic plates meet.
They were identified by concentrations of earthquakes.
What phenomena are associated with plate tectonics?
Things like Volcanoes and Earthquakes; they become more and more common the closer you get to the plate boundaries. Plate interiors are almost earthquake-free.
What was Alfred Wegener’s Continental Drift Hypothesis?
Pangea; a former supercontent that split into the continents we have now from continental drifts.
What were the Continental Drift Hypothesis’ 3 major evidence points?
- The fit of the continents (if you squish them together, they fit like a jigsaw puzzle)
- Distribution of fossils (fossils from specific animals were found in both Africa and South America where, if his hypothesis was correct, the 2 continents would’ve touched.
- Matching geologic units (Mountain ages and rock types are the exact same in North America, Greenland, Europe, and Africa.
It was not widely accepted because he had no credible hypothesis for ‘how’ the continents had moved.
Why was the continental drift hypothesis not widely accepted? Who later provided a framework for how they moved?
It was not widely accepted because he had no credible hypothesis for ‘how’ the continents had moved.
Henry Hess’s theory of Seafloor Spreading later provided an explanation.
What 2 things is the universe made up of? What are their definitions?
- Matter (A substance of the universe that takes up space and is made of mass, density, and weight.)
- Energy (The ability to do work that’s made of heat, light, and the pull of gravity.
What is the Hot Big Bang Theory?
A theory of the formation of the universe: It exploded in 13.8 Ga and has been expanding ever since. When the big bang happened, all the mass and energy was extremely dense and the temperature was more than 10 to the power of 32 kalvin. Galaxies didn’t form until 1-2 billion years after the big bang.
What is inflation?
The rapid expansion of the universe.
What is Nebula? Over time, what happens to it?
A rotating cloud of gas and dust.
Over time, it contracts and clumps. It condenses and becomes more dense; it starts collapsing because of gravity. These contractions and rotations will form a disk.
What is gas made up of?
Hydrogen and helium.
What is dust made up of?
Iron, magnesium, and silicon.
What is one light year?
The distance light travels in a year (9.46 trillion km)
What is a proto-sun/star?
A flat, rapidly rotating disk will form with the matter concentrated at the centre, and the matter in the middle is the proto-sum/star. When it collapses, the movement will increase the density, temperature, and rotation, and the energy can convert to heat or light.
What is the mass-to-energy conversion?
The sun ‘burns’ helium
657 tons of H/meter = 653 tons of He/minute
What is the protoplanetary disk?
The disk of remaining gas and dust where planets will eventually form.
What are planetesimals? How do they form?
They’re accretion of small clumps of dust.
Away from the Proto-sum, dust starts with coalesce and forms planetesimals, which clump into a lumpy protoplanet.
When did planets form?
Around 4.56 Ga
What does Homogeneous mean?
That it’s uniform all the way throughout; it has no layers.
What is the earth believed to be very similar to? What is it made with?
Chondrite meteorites.
They’re made with minerals like O, Si, Mg, Fe, and metals.
What are the 5 parts of early earth formation?
- During the middle-to-late stages of earth’s accretion, a Mars-sized body hit the earth.
- The giant impact propelled a shower of debris from both the impacting body and the earth into space. (125 parts were dispelled into space).
- The impact sped up the earth’s rotation, and tilted the ‘true north’ by 23 degrees.
- The earth re-formed as a molten body.
- The debris from the collision clumped together and formed the moon.
What has a very similar composition to the earth’s mantle?
Moon rock.
What are 3 sources of heat in the earth’s interior?
- Accretion. (From the objects that accreted to form earth)
- Compression (Compressing a planet under its own weight causes heat. The earth grew and increased in density and compression, causing the materials to heat)
- Radioactive Decay (Disintegration of radioactive elements. Elements decay to produce new elements, and some of this mass will turn into energy, which is heat)
What allows the earth to differentiate on the basis of density?
The earth partially melted.
What is the density segregation of liquids?
Iron and nickel blobs (the denser blobs) coalesce and migrate to the centre of the earth, and lighter silica-rich materials float towards the outer layers of the earth.
How many layers of the earth are there and what are they? What are their densities?
There’re 4.
1. The solid iron inner core
2. The liquid iron inner core.
(The above 2 are made of very dense iron in the centre of the earth)
3. The mantle
(Has very intermediate density)
4. The crust
(Has very low density)
Low density sinks to the core and high density floats to the surface. True or false?
False. Low density floats and high density sinks.
How did oceans form?
When the earth got cool enough, moisture condensed and accumulated to form oceans.
Photosynthetic Algae formed free oxygen around 3.8 Ga. True or false?
True.
What are the 3 goals of maps?
- To locate places
- To see patterns by looking at the distribution of geological features across a space/area
- To compare and contrast information