31 votes
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During the "Ice Ages" or "Snowball Earth" times, where was all the energy?

I'm not quite sure if the question is asking about glacial, ice ages, or snowball Earth, and whether it's about the onset or end of a glacial period. I'll try to hit all three. Ice Ages and ...
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23 votes
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Why are oceanic plates denser than continental plates?

Ocean lithosphere (geophysical definition of crust + upper mantle that acts as a 'plate') is primarily of basaltic composition - the upper levels are basalt and the lower levels are gabbro. The top ...
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  • 3,823
23 votes
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Why does sea level correspond to boundary between oceanic and continental crust?

Sea-level only sort-of corresponds to the oceanic–continental crust boundary. In depth, they don't correspond at all: It's the same story at an active margin: the plate boundary at a subduction zone ...
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23 votes
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What do continents "lay" on?

Matan, the continents where we all live "float" on the Earth's mantle. The continents are made out of relatively brittle rock called the "Crust" and the mantle is made out of much more ductile ...
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  • 947
22 votes
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Is there a geological explanation for the recent Mammoth tusk discovery 185 miles off the California coast?

The mammoth probably died on land. Its remains got picked up by a glacier. The glacier carried the tusk down to the sea. Eventually, the ice containing the tusk broke off as an iceberg. The iceberg ...
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  • 3,028
21 votes
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Why was the initial theory of plate tectonics so controversial?

One of the key aspects of plate tectonics is continental drift. The person who came up up with the theory of continental drift was Alfred Wegener. He published his theory in 1912. One of the issues ...
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20 votes
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Why is there a line of volcanoes along the northwest coast of North America?

The Cascades (the volcanic range that Mt. St. Helens and Mt. Ranier are a part of) are "arc volcanoes" (a.k.a. "a volcanic arc", etc). Volcanic arcs form at a regular distance (and fairly regular ...
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  • 1,276
20 votes
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What are some of the strongest theories against the existence of mantle plumes?

The best argument I've heard supporting strong skepticism of plumes, if not total dismissal, is that the theory is too flexible. To put it more bluntly, this amounts to saying that it is unfalsifiable ...
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20 votes

Is the Mid-Atlantic Ridge a ridge or a trench?

Trench has a specific meaning in plate tectonics. It doesn't just refer to any valley; it specifically refers to the features formed at subduction zones by the flexure of the downgoing oceanic plate. ...
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  • 2,201
19 votes
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How did Earth's plate tectonics start?

Is there a theory on how the Earth's plates were initially formed? The answer to this is has roots in another question you asked about the differences between continental crust and oceanic crust. ...
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  • 306
18 votes
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Equatorial bulge and tectonic plates

The plates are not as rigid as you think. You seem to be imagining the situation as something like this: I boil an egg and take the shell off in pieces, but I can't take a piece of shell from the end ...
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  • 5,380
18 votes
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What is the consensus among geologists about climate change being caused by humans?

First, a correction. Most climate scientists are climatologists rather than meteorologists. Climatology and meteorology, while related, are quite distinct sciences. Meteorologists and climatologists ...
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17 votes
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Is Mount Everest currently becoming taller or shorter every year?

According to one survey using GPS mounted on a plateau below the summit, Mount Everest is increasing its height approximately 4mm each year. As for plate techtonics, this site describes it pretty ...
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  • 2,688
17 votes
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How did the Ural mountains form?

The Ural mountains are one of the oldest mountain ranges on Earth. They started forming about 300 Ma ago by the subduction of the oceanic crust once attached to the Kazakhstania plate under the ...
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16 votes
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Is continental drift caused by lava pushing the seabed apart?

No, lava does not push the plates apart. The mid-ocean ridge basalt is passively filling the space left by the plates moving apart. Plate motion is driven by gravity (image by Vic DiVenere at ...
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16 votes
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Is there a reason most mountain ranges seem to run parallel to coastlines?

Mountain ranges are usually formed as orogeny where tectonic plates collides, known as convergent boundaries. The continental plates have less density than the oceanic plates and the buoyancy results ...
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  • 5,896
15 votes

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

Of course it isn't "absurd", and looking at the ball-park energy budget figures you'll see why: First, I don't think anyone is claiming the Earth is completely frozen. More of a "slushy at the ...
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15 votes

If we assume the mega impact hypothesis for the formation of Moon, where on Earth is the impact point?

I think you are confused about the timescales and the magnitude of the impact that is being talked about here. The collision between the early Earth and a roughly Mars sized body, Theia is thought to ...
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  • 2,201
14 votes
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What caused the bend in the Emperor/Hawaii chain of islands, 45 million years ago?

I don't recall this being considered a real 'mystery'. For decades after Tuzo Wilson's revolutionary Plate Tectonics the accepted explanation was of a change in direction in the plate motion over the ...
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  • 649
14 votes
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At what point does plate tectonics stop?

One permanent threat to plate tectonics is the oceans vanishing. The scientific jury may still be out on this matter, but most geologists and geophysicists consider water to be the lubricant that ...
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14 votes
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Plate Tectonics: Is it possible to have an ocean-continent divergent boundary

The oceanic plates are themselves formed from the divergent boundary, so probably not. Even if a new rifting occurred exactly at the boundary, the result would eventually be that the ocean floor ...
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  • 5,896
14 votes
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How could this pyramidal Mountain have been formed?

Such forms tend to be created by glacial activity, which, ahem, the ice-covered continent is known for. Much discussion of this in the related question in Skeptics: Are there three pyramids in ...
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  • 2,803
14 votes
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Why are the latest additions to the Hawaiian-Emperor seamount chain the highest?

As it was explained to me at university there are two factors; buoyancy and erosion. Rock buoyancy is a major factor, fresh Basalt is hot and dry and has a much lower density than older oceanic ...
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  • 4,227
13 votes
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What are the causes of the supercontinent cycle?

Please take into consideration that I am not a specialist of plate tectonics, just a paleontologist. Although this cycle is often nicknamed the Wilson cycle (probably because of Wilson, 1966), the ...
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  • 5,238
13 votes

Why was the initial theory of plate tectonics so controversial?

Why was the initial theory of plate tectonics so controversial? Plate tectonics was anything but controversial. A mere four or five years expired between its original proposal in 1963 by J.T. Wilson ...
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13 votes

Are the oceans rising or the continents going down? How can we know?

To the best of our knowledge, sea-level is rising because the volume of water is increasing. There is substantial local variation in sea-level change; it's falling in some parts of Canada. But of the ...
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  • 10.8k
13 votes

Why do some earthquakes and volcanoes occur within plates?

Crustal plates are not homogeneous, uniformly continuous rock masses with uniform stresses. They are a mixture of rock types with variable stresses and stress concentrations. They are also ...
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  • 20.3k
13 votes

Why are there no volcanoes where continents collide with each other?

Or is the continental crust too dry? Exactly this. Continental collision zones are actually full of volcanic rocks, which formed at the time before it was a continental collision zone. The Wikipedia ...
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12 votes

What properties must a rocky body possess in order to exhibit plate tectonics?

Plate tectonics appears to require multiple factors all arraigned in feedback loops. The planet must be large enough that it's surface to volume ratios is low enough to trap enough heat from ...
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