Most geological movies make an attempt at merging bad science and a poor plotline to make an overall pretty bad movie. The geology in this movie seemed mostly just a veil for an interesting storyline. Now I know most people had problems with this movie but I enjoyed it, although the science was "slightly" flawed. Now on to the geological review. I will also make time notes for what part of the movie that part of the commentary below is referring to.
- Geological Critique -
- The Story Basis -
The story's premise is that an asteroid hit the Earth 65 million years ago causing the extinction of the dinosaurs and that it is going to happen again. The plotline revolves around what would our society do today faced with a similar situation. How could modern technology save us? Or could it?
- Millions of Years Ago -
0:00:37 - The first sequence gives the background of the movie. The premise is that an asteroid hit the Earth 65 million years ago (mya) causing the extinction of the dinosaurs and that a similar even will happen again, perhaps causing our (the human race) extinction. When the intro begins, the first sentence starts describing that the view seen was the earth as it was 65 mya. According to the voiceover the planet was lush and fertile. Scientific information that we currently have indicates that this is true. So far, so good. The only problem is that the view shown is how the Earth looks today, not how it looked 65 mya. A significant amount time has passed
since that event took place and the continents were in different locations compared to where they are today.
The map to the right is an interpretation of what the geography would have looked like based on scientific research. A bit different then the map seen in the movie (Scotese.com). Mostly you can see the area around the Gulf of Mexico is not the perfect gulf that is envisioned in the movie and South America was not as close to the impact point as it is today. The dot indicates the location of the impact site and in the movie it is in the exact same location, the Yucatán Peninsula. So at least that was accurate.
- The Asteroid and the Impact -
0:01:04 - The asteroid in the movie is described as a piece of rock 6 miles wide. First off to interpret the movie asteroid, we need a few definitions of some extraterrestrial materials:
Asteroid - any of numerous small celestial bodies composed of rock and metal, 480 miles (775 km) to less than one mile (1.6 km) in diameter, that move around the sun (mainly between the orbits of Mars and Jupiter). Also called minor planet, planetoid. (dictionary.com)
Meteoroid - A solid body, moving in space, that is smaller than an asteroid and at least as large as a speck of dust. (dictionary.com)
Meteor - any of the small solid extraterrestrial bodies that hits the earth's atmosphere. (dictionary.com)
Meteorite - a mass of stone or metal that has reached the earth from outer space; a fallen meteoroid. (dictionary.com)
Comet - An object that enters the inner solar system, typically in a very elongated orbit around the sun. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water, or ice. (dictionary.com)
So based on the definitions, a 6 mile wide rock would in fact be an asteroid and it is not an unusual sight in the solar system. This is what actually is thought to have hit the Yucatán Peninsula 65 mya. So far, in general, the movie is pretty accurate.
The movie then goes on to state that the rock hit with the force of 10,000 nuclear weapons. To understand this you must understand that most objects in space are moving at a tremendous rate of speed compared with the Earth. When asteroids hit the Earth they are typically moving about 6 to 12 miles/sec, so even a small one will produce a big dent. The crater to the left, Meteor Crater in Arizona, was formed by a meteorite 150 feet across, or about 0.5% the size of the Yucatán asteroid. The explosive force produce during the Meteor Crater impact is considered to be about 2.5 megatons, or about 150 Hiroshima bombs, and produced a crater a mile wide (barringercrater.com).
The Chicxulub crater that was created from the Yucatan asteroid is 110 miles across and the estimates for the power resulting from the impact vary widely. They range from 100 million megatons (universetoday.com) up to a trillion megatons (oregonstate.edu). That is a very wide range of possibilities so one must take the high extreme with a grain of salt, since the majority of sources that I found quote the 100 million megatons, or somewhere within the ball park of that. So that is likely the best current estimate for the amount of power released during the impact.
The movie also compares the Yucatán impact to the explosion of 10,000 nuclear weapons. But when comparing them, do you compare it to the Hiroshima bomb or to the much larger modern day nuclear weapons? In comparison to the Hiroshima bomb, 10,000 nuclear explosions would be about 167 megatons. Far, far smaller than our current estimate of 100 million megatons.
Currently, most nuclear bombs that are made are less than 1 megaton, although a megaton bomb is easily possible (nukefix.org). So we will consider in the current day values that the Yucatán asteroid struck with a force of 100 million megatons. Still far less than the trillion megatons, but we will assume that is a wild card anyway. The largest nuclear weapon ever created was the Tsar Bomba (pictured right), which was designed to have a yield of about 100 megatons (nuclearweaponarchive.com). Using this bomb as a basis we would have an impact that would be about a million megatons (100 megatons times 10,000 nuclear weapons). Still, only 1% of the modern day estimate of 100 million megatons.
The range that we could produce with the movie statement shows that comparing something to a value such as nuclear weapon strength is a poor method of describing anything, since nuclear weapon strength is very variable. The most conservative measure of the asteroids impact strength of 100 million megatons seems the most accurate. By comparing this to 10,000 Tsar Bomba nuclear weapons, we would have our closest estimate to the size of the impact, which is still only 1% of the total actual strength. So, I feel that the directors were likely going for a much smaller impact strength when coming up with these number because otherwise they are not even close.
- Dust Cloud -
0:01:25 - When an asteroid this large strikes the Earth it is bound to send up a debris cloud far into the upper atmosphere (pictured left). When it is in the upper atmosphere, air currents quickly carry the dust cloud around the Earth, essentially
blanketing the Earth. According to the movie a trillion tons of rock and debris were sent into the atmosphere where it blocked out the sun for a 1,000 years. Although the amount of debris that an asteroid can produce is up for speculation, a trillion tons of debris compared to the size of the Earth in general is miniscule.
Now the blocking of the sun for a 1,000 years is probably a vast overestimate. Most estimates place the amount of time that the debris "blocked out the sun" as several weeks to months (webspinners.com). When debris is put into the atmosphere a majority of it is too heavy to remain air born so it falls out fairly quickly, whether it be within months or years. When the thick debris has fallen out the finer ash and dust particles can remain in the atmosphere for years or even decades (atmos-chem-phys.org), but the remaining finer dust would not block out the sun. So the over-estimate of 1,000 years is a tad dramatic.
What is interesting is that in the debris cloud is shown as a fire ball that envelops the Earth. Although not mentioned verbally, this is an important aspect into the science of an asteroid impact. After the impact, the debris that falls back to the surface would create a storm of rocky fireballs and the surface would be brought to a boiling temperature incinerating everything near the impact site (telegraph.co.uk). So the fact that there is a fireball wave that extends outward from the crater is accurate, how far it goes from the impact site is another matter.
The main problem is how far is the affected area. It is hard to tell in the movie but it appears that the fireball extends across at least a quarter of the Earth's surface. There are two types of fire clouds that emerge from the impact, a warm fireball and a hot fireball (diagram to the right). The warm fireball travels across the surface of the Earth for 100's of miles while the second fireball, the hot fireball travels further up in the atmosphere for 100's to possible 1,000s of miles. So could the fireball act like it did in the movie? It is possible. It mostly depends on how far it actually traveled. More than likely though, the movie overly exaggerated the dstance, but not by much I would say (plattsburgh.edu).
- Again? -
0:01:46 - "It has happened before, It will happen again." Definitely. Back early in Earth's history the planet was pummeled with meteors causing it to look similar to the moon. This is due mainly to the majority of debris left over from the formation of the solar system. Plate tectonics and active volcanism has a tendency to erase the evidence of the past so the Earth does not look as it did back then. Most of the asteroids and meteors that have hit the Earth since were from the partial formation of a planet between Mars and Jupiter, which got ripped apart by the gravity of Jupiter and is now just the asteroid belt. When the belt was fresh there was more debris to hit the Earth but since most of the rogue debris has crashed onto planets, there is not much left. Although there is a lot of asteroids still hanging out there and several chunks do pass close to Earth's orbit. It is only a matter of time until one of them hits us.