Questions tagged [earth-history]

Questions relating to Historical Geology.

Filter by
Sorted by
Tagged with
6
votes
1answer
510 views

How was the Earth formed?

What events took place in our Solar System which led to formation of the Earth? I have heard from sources that a big giant star exploded and the Earth was formed. Is this true ?
18
votes
3answers
2k views

Why deep ocean didn't freeze during snowball Earth?

I know that at least twice in its history Earth was totally frozen. I also know that the last time it happened there were already life on Earth, and it survived. In deep water, under the ice, which ...
11
votes
1answer
263 views

Is there conclusive evidence for the Antarctic Circumpolar Current developing after the glaciation of Antarctica?

The Antarctic Circumpolar Current (ACC) is the continuous oceanic current that encircles the Antarctic continent, as is often explained in the literature as being the cause of the onset of glaciation ...
11
votes
2answers
17k views

What is the tectonic setting for the formation of the Great Dividing Range in Australia?

Australia's Great Dividing Range is the largest mountain range on the continent, running down the length of the eastern part of the continent, as shown in the Geoscience Australia map as a dark line, ...
10
votes
1answer
130 views

What does geochemical data tell us about Earth's earliest palaeoclimatic conditions?

Given that the age of the oldest zircon samples are about 4.4 billion years old, and meteorites and other extraterrestrial samples can also give us some indication about the Earth's composition into ...
9
votes
1answer
286 views

Why is the concept of “mass extinction” a relatively recent development in geology?

The concept of "mass extinctions", with its catastrophic connotations, is a relatively recent development in the geological sciences. It evolved in the early 1980s, driven by two landmark publications ...
12
votes
3answers
353 views

What is the age of the earliest traces of life on Earth?

In the article Oldest rocks, earliest life, heaviest impacts, and the Hadean–Archaean transition (Moorbath, 2005), the author states (based on previous referenced research) that the $\ce{^13C}$ ...
10
votes
0answers
106 views

Where did the energy released due to gravitational binding energy of the Earth go? [closed]

The gravitational binding energy of the Earth is $2×10^{32} J $, so the same amount of energy must have been released during the Earth's history. According to this and this, the current internal ...
9
votes
1answer
1k views

Was volcanic activity more prevalent when the dinosaurs roamed?

Popular film culture often depicts much volcanic activity during the time of the dinosaurs. Assuming "time of the dinosaurs" as the Jurassic (200 million years ago) until the end of the Cretaceous (...
11
votes
1answer
242 views

What caused a fall in atmospheric oxygen about 1.9 billion years ago?

Using chromium isotopes geochemistry, Frei et al. 2009, describe in the article Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes that after the Great Oxidation Event (...
36
votes
5answers
3k views

How do we know the asteroids formed at the same time as earth?

In continuation of the question Why is Earth's age given by dating meteorites rather than its own rocks?, what evidence do we have that the asteroids indeed formed at the same time as earth? Is there ...
12
votes
2answers
1k views

Have meteorites been found in the oldest sedimentary rocks?

Dropstones sometimes occur in sedimentary rocks. These are foreign rocks and boulders that happened to "drop" into a sediment and were fossilised when the sediment was lithified. (source: Michael C. ...
33
votes
3answers
14k views

Why is Earth's age given by dating meteorites rather than its own rocks?

Reading a course on Precambrian, I read that: Earth Age (around 4.5 billion years) is dated thanks to the meteorites hitting Earth during its formation rather than the inner materials composing the ...
10
votes
1answer
246 views

'Late Veneer' on other planets

Is there any evidence of external material source events, like the 'Late Veneer' on other planets? Or is this theory specific just for Earth? Note, that this question may be related to How and why ...
8
votes
3answers
393 views

How do archaeologists address time dilation when analyzing carbon dating results?

It is a proven fact that the gravitational force exerted upon an object directly affects that objects experience of time; the greater the gravity, the slower time passes, and visa versa. While the ...
18
votes
2answers
800 views

Why are minerals found in “large” quantities and not scattered throughout the earth as individual atoms?

Heavier elements are created in stars. After stars die they scatter these heavier elements throughout the universe. These elements eventually gather to form planets. But why do we find "chunks" of ...
26
votes
4answers
11k views

What is the origin of the dominant atmospheric nitrogen content in Earth's atmosphere?

Comparing the atmospheric compositions of Earth with our nearest neighbours: As the table shows, the Earth's atmospheric nitrogen concentration is 78%, compared to 3.8% for Venus and 2.7% for Mars ...
11
votes
1answer
1k views

How old is Casiquiare canal?

Casiquiare canal is the world's largest bifurcation. Since such a large bifurcation seems unlikely to be produced and even less likely to stay for centuries, I wonder how old it is and why all the ...
25
votes
1answer
656 views

How much have global GPP and biomass changed over Earth's history?

I'm curious about how much is known about this topic: how much has the total amount of life on Earth changed over the 4 billion years or so that it has existed on this planet? Are there estimates of ...
7
votes
0answers
65 views

How much does ocean cover percentage change between glacial periods? [duplicate]

Currently, oceans cover about 71% of the total area of Earth. Ice ages can cause this figure to fluctuate, by lowering the sea level and creating land bridges and other features. How much can this ...
25
votes
5answers
5k views

During the “Ice Ages” or “Snowball Earth” times, where was all the energy?

We often seem to accept the idea that there were periods of time in which the entire surface of Earth was frozen, for the most part. This implies that there were periods of time in which the entire ...
15
votes
1answer
355 views

How did helium deposits form?

I always wondered, because helium gas is so lightweight, how did it get into the deposits like the ones that people tap? Is it formed underground, or was it trapped?
11
votes
1answer
412 views

How long did it take for Earth's magnetic field to first appear?

Merely what the title states. My knowledge of geography/geology/*logy is limited to high-school, and some snippets, and snatches of conversation. As I understand Earth's magnetic field is attributed ...
12
votes
2answers
462 views

Determining the paleoelevation of mountain ranges

In New Delhi, a lot of people say that the Aravali range used to be as tall as the Himalayas. How do scientists know that some mountain range used to be a lot taller millions of years ago, and what ...
7
votes
1answer
337 views

Historical atmospheric partial pressure & Henry's law constant

The explanation given for the fact that temperature has historically led CO₂ levels is Henry's law. Figure 1: Vostok ice core records for carbon dioxide concentration (Petit 2000) and temperature ...
7
votes
1answer
117 views

Who originated Taylor's axiom of lunar formation, and where?

I've been doing a bit of reading about the formation of the moon, and I've found multiple references (1, 2, 3) to something called Taylor's axiom, stated in link (3) above as: The best models for ...
7
votes
2answers
1k views

Life on Earth previous to us

I've seen in several places that there seems to be an extinction cycle on Earth of approximately 27 million years. I've read this here: http://www.dailymail.co.uk/sciencetech/article-1294372/Life-...
14
votes
1answer
123 views

In what sense did the Oklo reactor “trap” its own nuclear waste?

A number of popular writings on the natural fission reactor at Oklo, Gabon (e.g. here) state that some of the energetic byproducts (krypton and xenon, presumably 85Kr and 133Xe) of the reactor were "...
11
votes
1answer
289 views

Regarding the theory of the origin of water on Earth through meteorites, why wouldn't the water evaporate on impact?

Water on earth has been theorized to have come through comets trapped inside crystals. But why wouldn't that water evaporate on impact, and wouldn't the atmosphere at that time allow the vapours to ...
18
votes
2answers
1k views

Historically, how has the fraction of Earth covered by water changed?

Today, 70.8% of the Earth is covered in water (± a few tenths of a percent depending on how you account for lakes).1 How has this figure changed over the history of the Earth, and why? Of course, if ...
10
votes
1answer
167 views

Sediment layer chronology

In the new Cosmos series, Neil DeGrass Tyson in explaining different ways the age of the world has been determined, shows how sedimentary layers at the Grand Canyon are a fossil record of a lot of the ...
7
votes
1answer
833 views

Is a billion years of Earth's history missing?

Appears that a 4.4 billion-year-old crystal is oldest piece of Earth, and the crystal's chemistry -- specifically, the ratio of oxygen isotopes within it -- suggests that the temperatures on Earth 4.4 ...
5
votes
2answers
6k views

Are there more earthquakes near the equator or poles?

When comparing the average distance of the all known earthquake epicenters to the nearest pole, is the longitudinal distance to the equator or the poles the smallest of the two? Please note that any ...
8
votes
2answers
1k views

Why is earth's axis tilted?

Why is the axis of earth tilted? It can't possibly be that the Northern hemisphere is larger causing it to be pulled toward the sun, because then it would always be summer in the N hemisphere and ...
18
votes
3answers
29k views

Why does the earth spin clockwise?

Why does earth rotate in a clockwise direction? Did a large meteor collide with earth causing earth to rotate? If that is what happened, could another, larger meteor cause earth to reverse its ...
14
votes
3answers
2k views

Is Earth an organism?

According to Wikipedia, "all known types of organism are capable of some degree of response to stimuli, reproduction, growth and development and self-regulation via homeostasis." Further, watching a ...
25
votes
3answers
35k views

Why is Earth's inner core made of an iron-nickel alloy?

This question has puzzled me for a while. I know that earth's mantle is made of different minerals, metals and rocks etc. and that has always made complete sense to me. But why is the inner core made ...
17
votes
3answers
3k views

How did Earth's plate tectonics start?

Plate tectonics is a theory which describes Earth's lithosphere as being composed of distinct plates which are able to move atop of the underlying asthenosphere. At plate boundaries, this movement ...
20
votes
2answers
960 views

How are the banded-iron-formation iron-ores formed?

Many of the richest and purest iron ores are found in so called banded iron formations, cm thick magnetite or hematite layers intermixed with iron poor rock layers. Since these are usually of pre-...
14
votes
3answers
270 views

How have global sedimentation rates changed over the last billion years?

Do we have a graph of how sedimentation rates changed over time?

1 2
3