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Questions tagged [earth-history]

Questions relating to Historical Geology.

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9
votes
1answer
116 views

With so many positive feedbacks accelerating global warming, how did the earth ever re-enter ice ages after it came out of one?

We hear a lot about positive feedbacks when it comes to global warming. For example: ice reflects solar radiation, so as the ice melts more solar radiation is absorbed which accelerates warming; ...
0
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1answer
33 views

How can radiometric dating of meteorites determine the age of the earth? Wouldn't this only determine the age of the decaying nuclide in each rock?

How can the radiometric dating of different meteorites determine the age of the earth? Wouldn't radioactive decay have already been occurring in all of those meteorites long before they hit earth? ...
2
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1answer
51 views

Do earthquakes produce folds on rocks?

Earth rocks are frequently folded at surface. Folds in alternating layers of limestone and chert in Crete, Greece. Source: commons.wikimedia Are earthquakes the main mechanism ...
2
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1answer
113 views

How Good is The Evidence For Snowball Earth?

Some geologists say there were times between 770 million years BP and 630 million years BP when ice ages were so profound that the Arctic and Antarctic ice caps met at the equator. This is called the ...
5
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2answers
105 views

Molten salt seas on the future Earth

As the sun gets brighter, the oceans are expected to evaporate by the next billion years or so (the vapor slowly gets stripped off into space). The salt, which is less dense than most rocks, will be ...
2
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1answer
84 views

Which ocean is going to be swallowed by the Supercontinent Cycle, Atlantic or Pacific?

The register shows several supercontinents have been formed on Earth's History: "The most recent supercontinent, Pangaea, formed about 300 million years ago (0.3 Ga). There are two different ...
3
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2answers
113 views

Why is the bedrock buried so deeply in much of northern Minnesota?

Although parts of northern Minnesota have bedrock exposed at the surface (especially in the Boundary Waters area and along the short of Lake Superior), the more usual situation here is for the bedrock ...
4
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0answers
31 views

Age of the Earth without radiometric dating?

It is common knowledge that age of the Earth is roughly 4.5 billion years. Radiometric dating of meteorites (which were formed during the formation of Earth) and earliest rocks on Earth have both ...
1
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0answers
35 views

Has biology's influence in CO2/Phanerozoic variations been decisive?

I must say I always as geologist have explained myself CO2 changes at Earth's History in terms of Wilson Cycle. And I always thought biosphere is adapted to geology. But from two questions I link at ...
3
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0answers
32 views

Biomes that existed during the Paleocene-Eocene Thermal Max (PETM)

I understand that you could fill multiple books with descriptions of the PETM and the mechanisms that incited the event. I have always wondered what regions of the world were covered in what types of ...
3
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0answers
31 views

Where did the heiltsuk's find obsidian?

The discovery of hearths and other carbon dated items on an island off the north east coast of Canada puts modern humans there 2,000 years before the Alaskan land bridge existed. The glaciers of ...
5
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2answers
156 views

How much climate history can be reconstructed using marine sediment cores?

Today I learnt in college that marine sediments can be used to reconstruct the climate up to 500 million years back. I find that number very strange because in another class we learnt that the ocean ...
1
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2answers
219 views

Why is a future increase in solar luminosity by 10% supposed to have disastrous consequences for life on earth when the last 30% did not?

One remarkable thing about the climate history of earth is that despite the fact that solar luminosity was fully 30% lower in the beginning, temperatures were actually quite close to today. Since then ...
2
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3answers
330 views

Why Do Supercontinents Form? [duplicate]

It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future. ...
6
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1answer
93 views

Historically, how did the total amount of salt / NaCl on Earth develop?

After reading this question about the origin of NaCl on Earth, I'm wondering: How did the amount of NaCl develop historically? Is it a more or less linear growth until today? Was it such a linear ...
3
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1answer
114 views

What was the percentage of land mass in prehistoric times when temperatures were high enough that we had no ice caps?

I grew curious after watching a presentation about the large creatures of prehistoric times. One of the theories cited about why creatures were so big was the increased oxygen in the atmosphere due to ...
14
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5answers
3k views

Could the earth be much older than the currently accepted number?

According to wikipedia, the Earth is about 4.543 billion years old. If I understand correctly, this number is based on radiometric age-dating of meteorites. So basically, the logic is this: We've got ...
9
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1answer
2k views

When did wildfires start to occur on earth?

An oxidizer, fuel, and heat are needed for a fire. When considering oxygen as the oxidizer, an oxygen concentration of approximately 16% is required for combustion. Plant material is the fuel ...
3
votes
1answer
134 views

Ocean water coming from Mantle vs coming from meteorites

Posibly duplicate from Water on Mars and Earth I remember well a hydrology course where our teacher made some calculations of the total flux of water from Mantle ejections in Earth's history. He ...
4
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1answer
675 views

Causes of fluctuations in atmospheric oxygen in past 300 Mya

I have two questions based on the history of atmospheric oxygen levels depicted below. Source: https://commons.wikimedia.org/wiki/File:Sauerstoffgehalt-1000mj2.png. The notes below the chart explain ...
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0answers
19 views

Mass contribution during the LHB

How much mass (either absolute or relative to the Earth) was [estimate to have been] added to the Earth during the Late Heavy Bombardment?
2
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1answer
108 views

How many times in total has Earth formed a super continent?

I know there was a Pangaea at one point in history that broke into the continents of today, but I could have sworn there was another instance in Earth's history that there was a super continent, maybe ...
2
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1answer
114 views

Where did the carbon, neon and nitrogen go?

It is interesting to compare estimated Earth abundances with estimated Milky way abundances. Obviously the hydrogen and helium were gaseous and too light for Earth's gravitational field (other than ...
8
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4answers
452 views

Before the Great Oxygenation Event, where was the oxygen?

Today, the oxygen in the atmosphere is about 1018 kg. The estimated carbon biomass of the earth is about 4×1015. Less than 0.5%. Estimated fossil fuels are around 5 times as much as existing carbon ...
8
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0answers
231 views

How much heat flow is needed to maintain plate tectonics?

The Earth is emitting about 47 terawatts of heat energy, producing a heat flow of 0.0921 W/m$^2$ due to radiogenic and primordial heat energy. The heat flow drives mantle convection which in turn ...
-1
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1answer
240 views

If Earth had rings would gravity exerted by Earth decrease?

If Earth had enough mass in its own rings, more than the weight of Earth: What could it decrease the gravity to? Would the atmosphere have more depth or be thinner? What would the weather be like? ...
11
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1answer
1k views

What is the fastest the Earth has ever spun?

How fast can the Earth rotate and support life? In prehistoric times, dinosaurs were so massive that archeologists wonder how they were not crushed under their own weight. Could a faster spinning ...
11
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2answers
162 views

Water on Mars and Earth

If water on Earth came from meteorites, why doesn't Mars have substantial water? What made it more highly probable on Earth than on Mars?
3
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0answers
302 views

Puzzle using relative dating principles

This isn't directly looking at a real life ecological example kind of thing, but it requires knowledge of relative dating, so I thought I would come here. Here is what was told: -"Worms" (curved ...
8
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1answer
1k views

What would it be like to live in an ice age?

If you were born in the most recent ice age, how different would your life be compared to how you live it today? Furthermore, if humans currently lived in an ice age, how would it affect life today?
4
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1answer
99 views

What is a “tar shower?”

I'm reading about Sodom and Gomorrah on Wikipedia when I come across this: "One such idea is that the Dead Sea was devastated by an earthquake between 2100 and 1900 BCE. This might have unleashed ...
8
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1answer
146 views

Earth and moon have different mantle compositions. Is this a fatal flaw in the 'Giant Impact hypothesis'?

Deep impact ejecta on the moon seem to indicate that the moon's mantle is predominantly 'low-calcium pyroxene' (recent letter to Nature), whereas the Earth's mantle (or at least the upper mantle) is ...
0
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1answer
108 views

Can someone provide a map of Nazca lines with this image in it?

I found this image of a bird with another image below its right wing on google earth in nazca peru. Is there any maps or infomation available that can help me identify this one? Kind regards Jeff B.
2
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2answers
562 views

Was the Earth's sea-level significantly lower in ancient times?

A lot of times, ancient artifacts or even whole ancient civilizations are found buried very deep into the ground surface of the earth. Entire civilizations that had high buildings have been found ...
1
vote
1answer
47 views

Approximation of ancient landmasses using current ocean floor data

I am wondering how accurate such an approximation would be. I wish to take a current height map of the earth (including the ocean floor) and approximate the form of ancient landmasses by changing the ...
1
vote
2answers
285 views

Earth's orbit and historical sun-earth distance

Purpose of my question: I create program to calculate solar radiation and I need to calculate radius between sun and earth. The based on book "Guide to HTML, JavaScript and PHP" For Scientists and ...
2
votes
1answer
41 views

Sediment boundarys produced by largest meteors? Vredefort, Sudbury and Chicxulub

Chicxulub crater is the third largest crater on earth, which is said to have produced the KT boundary. What is the sediment layer produced by the 1st and 2nd largest craters? Also, there many ...
15
votes
1answer
4k views

How old is the Earth?

According to most articles I've read online, the estimated age of Earth is 4.5 billion years. Question: How old is the Earth? So I actually want to confirm that this is the case. Maybe there are ...
1
vote
1answer
111 views

gamma ray burst, extinction-level event

From this subsection in Wikipedia's aricle on extinction event: A nearby gamma-ray burst (less than 6000 light years away) would be powerful enough to destroy the Earth's ozone layer, leaving ...
4
votes
0answers
143 views

Did Theia collide directly with proto-Earth?

I was learning about the formation of Earth on Kahn Academy where it was mentioned that a protoplanet named Theia had a glancing impact with the earth and formed the moon. It seems like there is also ...
3
votes
1answer
566 views

How much energy released by the Theia-Gaia impact?

I read somewhere that the Chicxulub impact released the energy equivalent of anywhere from 100-300 teratons of TNT. That's an impressive amount of energy. Assuming a head on collision (according to ...
2
votes
1answer
146 views

Is there any place on Earth that is permanently a desert?

I am interested to know if there is any place on Earth that is permanently a desert (except Antarctica). By permanent I do not mean to be the physical meaning of forever. It means the place has to be ...
7
votes
2answers
380 views

What fraction of Earth's crustal material survives the supercontinent cycle?

I know that things are not as simple, but for the sake of argument I'll assume a supercontinent cycle of $\sim$400 Myr periodicity is active on Earth. If that is the case, then my naive ...
7
votes
1answer
325 views

A circle shape in Madagascar

I was seeing Madagascar on Google Maps and accidentally i saw a circle shape near Bebao. Coordinates are 17.4317443°E and 44.644248°S. Please, to satisfy my curiosity, can you tell me why is this ...
8
votes
1answer
2k views

For how long has the Earth been habitable for humans?

Let's imagine that a human (male or female) could be sent to the past, anytime after the birth of our planet. What would be their survival probability over time? If this question is too hard to ...
4
votes
1answer
233 views

Surface temperature in early hadean period

I am considering earth's internal heat budget for a project in university. For this I need an estimate on the temperature of the earth shortly after it had formed. In Kelvin's On the Secular cooling ...
6
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0answers
197 views

1950's - 60's Earth Science

I'm writing some lore for a fictional world, which is set in the 50's early 60's roughly. One thing I'd like to bring is a fairly grounded explanation for the creation of the planet and the universe, ...
3
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0answers
226 views

Pangaea, supercontinent formation and fragmentation [duplicate]

Is there a widely accepted model for the supercontinent cycles ? From the novice point of view, it is not obvious why the continents would be fragmented all over the earth as now, but 300 millions ...
1
vote
2answers
649 views

Speed of tectonic plate movement

I'm doing some research about tectonic plates and at which speeds they move and in which directions, because I'm writing a program to simulate the movement of the tectonic plates and also calculate ...
6
votes
1answer
569 views

The age of tectonic plates

There is information which says that East European Platform sticks out at the Baltic Sea and, therefore, we can see the ordovican layer in Estonia whereas ...