Snowball Earth The surface of the earth was below 0 degrees C 2.3 billion years ago. Doesn't this imply the earth wasn't really that hot when it was formed? Can anyone tell me what the surface temperature of the earth was 4.3 billion years ago?
I don't think so. Isn't this really just like making a Baked Alaska in reverese. Hot on the outside, ice cold on the inside. I suppose a Beef Wellington would be a better example. The heat of the Earth's formation is all trapped inside, coming out only very slowly. I think I read somewhere that the total heat flow from the Earth's interior in a year would not be enough to melt a layer of ice 1cm thick, so the interior temperature really won't have that big an effect on the surface temperature. So, Snowball Earth doesn't cause a problem for a hot Earth formation, or for the interior temperature remaining high today, which we know it is. No. Is it important? Interesting, but I don't see how it ties in to Snowball Earth and hot formation theories. I mean the temperature can drop pretty fast at night. I remember out in the desert, without cloud cover, it can get chilly really quickly.
Not that important, I've wondered about the cooling model for the earth. An ice age at half-life seems rather odd before the evolution of life began.
A reverse baked alaska really. Since all "cells" come from the sun, it would be hot in the core and cold in the icy universe. Wouldn't the heat come from it's nucleus? If the earth started as an ice ball, it would still be one wouldn't it? What could dig so far down to give it heat? An asteroid hitting the earth and combining gas to produce electrical current to "create" the magnetic shield to protect the earth?
All I can say, protostar, is that you seriously lack knowledge in Earth's geohistory. Let's just say that even (if we forget everything else) Earth would have been an ice-ball (which it wasn't) first hundreds of millions of years of its' existance, then the collision between Earth and a Mars sized object about 4 billion of years ago certainly turned our planet into one huge ball of boiling magma when it fused with the other object. During that event our Moon was created.
Another Snowball Earth has also been proposed for the first known ice age, 2.3 billion years ago. There the proposed mechanism is the first appearance of atmospheric oxygen, which would have absorbed any methane in the air. As methane is a powerful greenhouse gas, and as the Sun was notably weaker at the time, temperatures plunged. Earth had no naturally occurring oxygen until life created it. After this ice age, life could have maintained itself near hydrothermal vents.
Heh, I didn't even see that, Woody in my ignorelist. Of course, spidergoat is right. p.s. Anyone interested in Snowball Earth, there is a BBC Horizon program on the topic. They also discuss the ways on how life probably survived during that period. You can download it through BitTorrent here: http://www.mininova.org/tor/71905
I always had the impression that the earth was like a sauna when life began and then it gradually cooled down where we are starting to have ice ages.
evidence that the McGinnis Glacier, a little-known tongue of ice in the central Alaska Range, has surged. Assistant Professor of Physics Martin Truffer recently noticed the lower portion of the glacier was covered in cracks, crevasses, and pinnacles of ice--all telltale signs that the glacier has recently slid forward at higher than normal rates. The New Zealand Department of Conservation is worried that someone will be killed as giant chunks of ice fall from rapidly advancing glaciers. The risk of ice collapse at the face of the Fox and Franz Josef Glaciers is high A report from the University of Swansea's School of the Environment and Society said that two major Greenland glaciers - the Kangerdlugssuaq and Helheim glaciers - have doubled their rate of flow to the ocean over the past two years after steady movement during the 1990s. So, another ice age coming upon us?
Isn't it the case that rapid glacier advance can be evidence of rising temperatures? The higher temperature increases the amount of sub-glacial water, which lubricates the glacier-ground interface and so encourages more rapid movement.
The Earth's surface cooled quite quickly after the Earth formed. chemical data from the oldest terrestrial mineral known, a 4.4 billion year old zircon crystal, show there was already oceans by then. The very early atmosphere was similar to Venus's present atmosphere (but the sun was 30%-40% dimmer then because fusion causes the suns core to become denser, increasing fusion rates; the dimmer sun and greater distance from the sun compared to venus kept the earth suface below the boiling point). The vast majority of the CO2 that made up most of the early atmosphere became trapped as limestone during the first 500 million years, leaving an atmosphere dominated by Nitrogen with some CO2. When methanogenic bacteria (Archaea, really, but i'm used to using the term "bacteria" for both archaeans and eubacteria) evolved the methane they produced kept the temperature high enough to prevent an ice age. when cyanobacteria statrted pumping out oxygen they oxidized the methane and the temperature dropped big time. Oh, and the Early Proterozoic Snowball Earth wasn't the first ice age. I read this article about an earlier ice age in the late Archean.
One of the difficulties that some may be having on this thread is confusion between the temperature of the atmosphere and surface (which have varied and continue to vary dramtically over geologic timescales), and the temperature of the interior of the planet (stable and changing only slowly and in a consistent direction over time). Once the effects of heavy bombardment had ended, the progression of interior temperature has been steadily downwards. Surface temperatures, ibn contrast, have fluctuated by large amounts as variations in solar radiation, atmospheric composition, continental postions, global wind patterns, cloud cover (albedo), oceanic circulation, etc have interacted.
Yes and wouldn't the earth taking a more oval eliptical path around the sun have something to do with it as well? since the path will be more oval and longer time away from the sun, it would produce a colder earth for longer periods of time. Maybe the eliptic path only goes very oval every 25,000 years or such but 2.3 billion years ago it went its farthest distance. Thats why that ice age was so cold. Just a thought.
"Even in geology, it's not often a date gets revised by 500 million years. But University of Florida geologists say they have found strong evidence that a half-dozen major basins in India were formed a billion or more years ago, making them at least 500 million years older than commonly thought. The findings appear to remove one of the major obstacles to the Snowball Earth theory that a frozen Earth was once entirely covered in snow and ice - and might even lend some weight to a controversial claim that complex life originated hundreds of million years earlier than most scientists currently believe." Read more
Heh! I work there - in that very department no less - and missed that one completely! - mind you even though they merged the geography and biology departments into one "school" the biologists and geographers still refuse to talk to each other - let alone listen to each other - typical scientists eh?! Please Register or Log in to view the hidden image! I'm guessing that it was John Heemstra who was responsible for this report - I had to attend some of his lectures on glaciology as an undergrad and from the ones I managed to stay awake in (yes he's one of those lecturers) I recall that he was very quick to point out that one of the major problems with tracking glacial advance/retreat in places like Greenland (particularly Greenland in fact) is the lack of scientific stations and expeditions for long-term monitoring and the lack of population for even gaining anecdotal evidence - so I'd be interested to know where and how he got his data. Secondly, are you sure the report says what you think it says ? - for example I spent last summer in Alaska where the majority of glaciers -certainly every one I visited, is retreating - however their rate of input to the ocean has increased - because they are melting and calving into the ocean at a greater rate. Got a link? here's me at the Shoup Glacier in Prince William Sound, which has retreated something like 5km in the last 30 years apparently - where it used to encroach out into the sound, you now need to walk or paddle up a ravine for a couple of miles before you get to it. Please Register or Log in to view the hidden image! Please Register or Log in to view the hidden image! Yes - it was cold in the kayak - but not half as bloody cold as the night I spent camped below it - thank the big pink pixie in the sky that I brought me friends captain morgan and jack daniels along
