What is A Meteorite Strewnfield?
To understand what a meteorite strewn field is you must first understand what a meteorite is and how it ends up on the Earth.
Meteorites are fragments of asteroids and meteoroids which have impacted the Earth. This debris, at one time was floating around the solar system orbiting the Sun. Most of this material is located in the asteroid belt between Mars and Jupiter. From time to time asteroids within the asteriod belt bump into one another effectively changing their orbits. Eventually some of this material loses it’s orbit around the Sun and is pulled into Earth’s atmosphere by the massive forces of our planets gravitational field.
Once a meteoroid or asteroid enters our atmosphere it’s subjected to extreme pressure and heat which produce the phenomenon known as a meteor or fireball. The high rate of speed at which the body is traveling coupled with the enourmous strain these pressures excert on the asteroid can cause it to break apart into hundreds of smaller pieces. Some pieces can still be rather large and weigh many kilos or even tons depending on how large the original asteroid is, but most are small in size usually just a few grams in weight.
The Peekskill Fireball & Meteorite Impact Video
Most meteors are caused by small meteoroids no bigger than a grain of sand and never reach the ground, burning up in the upper reaches of our atmosphere before they can impact Earth’s surface.
When a larger piece of debris collides with our planet sometimes it can survive the trip all the way to the ground.
A large meteoroid or small asteroid made of stone can produce a large fireball visible from the ground from hundreds of miles away.
Typically it will flash a bright and brief fireball, break apart high above the Earth, blink out and then fall invisibly to the ground.
While in flight an asteroid that breaks apart will incandesce until is slows below what scientists call cosmic velocity. This is tremendously fast and can be from 10,000 mph to 50,000 mph or more.
The asteroid will reach a point in our atmosphere where the air acts as a braking mechanism and slows the descent. The extreme pressures can break the asteroid apart into many pieces in a few milliseconds and brilliant flashes of light called the terminal burst point.
At this point the asteroid fragments, blinks out and is no longer incandescent. It’s now in a stage of of atmospheric entry known as dark flight.
At this stage the fragments are traveling at terminal velocity, usually no more than a few hundred miles an hour. Not fast enough to produce the energy and pressures to incandesce.
Larger pieces will travel further than the smaller lighter pieces which fall first since they lose their inertia faster than the more massive pieces. The resistance or drag produced by the debris passing through the air slows the smaller pieces first since they have less mass. The larger pieces can continue on much further after the smaller pieces have already impacted the Earth.
If a meteoroid falls at a very sharp angle then the strewnfield it produces will be smaller and harder to locate as the material will be spread over a smaller distribution elipse. Picture a handful of rocks thrown straight at the ground. They won’t cover much area at all. But if you throw a handful of pebbles straight out in front of you the distribution ellipse becomes much greater in size.
A Meteorite Strewnfield
A strewnfield is a section of ground (usually in a long elliptical or semi-circular shape) covering a few square miles where “two or more” meteorites of the same type and class fall and have been recovered. Most strewnfields are smaller 1/2 to a few miles in length and width. Some can be as large as 1-10 miles long and 1-5 miles wide. Meteorite strewnfields like the one shown in the video below are even smaller. There are also single stone meteorite falls which don’t produce a strewnfield.
Typically, the larger a meteoroid or asteroid is that enters our atmosphere the larger the strewnfield is. Not all meteoroids and asteroids break up when entering the atmosphere but when they do the length and width of a meteorite strewnfield depends largely on the angle of decent, speed at which the meteoroid is traveling and the compositional mass of the body. In other words, the heavier it is and the faster it’s going the further it will travel at a shallow angle of decent, thereby producing a large and long distribution ellipse where debris may be found on the ground.
The Elusive Meteorite Strewnfield
Finding a meteorite strewnfield is perhaps the holy grail of meteorite hunting. Meteorite hunters dream of finding their own meteorite strewnfield because of the personal satisfaction and sheer excitement of finding such a rare thing. Meteorites are rare. Very rare. Finding one meteorite is hard enough, but to find two in the same area is even more rare. Finding an entire meteorite fall area where meteoritic material has fallen over a wide area is a superb achievement.
Below is a graphic depicting a distribution ellipse and the pattern in a which meteorites typically fall. For the example we’ve used artistic license on the physics of it but this is how meteorites are usually dispersed over a wide area when a meteor or large fireball event turns into a meteorite fall. Debris from the meteoroid falls over a wide area sometimes tens of miles long and a mile or more in width.
Below is an atypical case of a very small meteorite “strewnfield” if you can call it that. This particular area was found by Ruben Garcia, better known as Mr. Meteorite, a professional meteorite hunter who lives and hunts in Arizona. The location of the meteorites found in the video is southern California. Visit Ruben’s Site Mr-Meteorite.net
Read the article here on Meteorite.com
Discovering a California Meteorite Strewn Field (Part1)
This meteorite hunting article originally appeared in the Feb. 2007 issue of Meteorite Magazine by Ruben Garcia
Since meteorites are so rare and if you do find a real meteorite, mark the spot and be sure to search the entire area where you found it. You may have found only a single meteorite from a single fall, but there’s a small chance you might just have discovered what scientists and veteran meteorite hunters call a meteorite strewnfield!
Read more about meteorite strewnfields:
BUZZARD COULEE METEORITE STREWNFIELD: (CANADA) Here is the info and data gather on the Buzzard Coulee meteorite strewnfield near Edmonton. Meteoritical Bulletin Entry for the Buzzard Coulee meteorite in the Meteorite Database
TAMDAKHT METEORITE STREWNFIELD: Here is some information on the now world famous Tamdakht Meteorite Fall in Morocco. Tamdakht Meteorite Hunt on Meteoritica.com
Other Meteorite Falls & Strewnfields & Meteorite Hunting from Mike Farmers Site:
- Moss, Norway (CO3.6) July, 2006
- Muonionalusta, Sweden (Iron) July and August, 2006/2007
- Cali, Colombia (H/L4) July, 2007
- Puerto Lápice, Spain (Eucrite) September, 2007
- Carancas, Peru (H4) Crater-forming impact September, 2007 (Rare Meteorite Crater Forming Event)
- Ash Creek Texas (L6) February 15, 2009
The Great West Texas Meteorite Hunt Geoff Notkin’s Blog
Meteorite Men Official Website – Steve Arnold & Geoff Notkin
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Credit/link should read “What is a meteorite strewnfield? – by MeteoritesUSA.com“
Asteroid Belt Graphic Source: Wikipedia – http://en.wikipedia.org/wiki/File:InnerSolarSystem-en.png
Meteor Streaking Through Night Sky Source: Wikipedia http://en.wikipedia.org/wiki/File:Leonid_Meteor.jpg