|
RIES-IMPACT [English]
The Nördlinger Ries is a
large circular depression in western Bavaria, Germany, located
north of the Danube in the district of Donau-Ries. The city of
Nördlingen is located about 6 kilometers (3.7 mi) southwest of the
centre of the depression. The word "Ries" is not a German word; it
is believed that the term is derived from Raetia, since the tribe
of Raetians lived in the area in pre-Roman times. The addition
"Nördlinger" is actually redundant, as there is no other place
called Ries. Ries impact crater The depression is interpreted as a
meteorite impact crater formed about 14.3 million–14.5
million years ago in the Miocene.
The crater is most commonly referred to simply as
the Ries or Ries crater. The original crater rim had an estimated
diameter of 24 kilometers (15 mi). The present floor of the
depression is about 100–150 meters below the eroded remains
of the rim. It was originally assumed that the Ries was of volcanic
origin.
In 1960 two American
scientists, Eugene Shoemaker and Edward Chao, proved that the
depression was caused by meteorite impact. The key evidence was the
presence of coesite (shocked quartz), which, in natural
unmetamorphosed rocks can only be formed by the shock pressures
associated with meteorite impact. The coesite was found in the
building stone (suevite) of the Nördlingen town church, constructed
from locally derived stone.[3] Two petrographical papers of
Johannes Baier have shown that suevite was formed from mesozoic
sediments. Another impact crater, the much smaller (3.8 km
diameter) Steinheim crater, is located about 42 kilometers
west-southwest from the centre of Ries. The two craters are
believed to have formed nearly simultaneously by the impact of a
binary asteroid.
Recent computer modeling of
the impact event indicates that the impactors probably had
diameters of about 1.5 kilometers (4,900 ft) (Ries) and 150 meters
(490 ft) (Steinheim), had a pre-impact separation of some tens of
kilometers, and impacted the target area at an angle around 30 to
50 degrees from the surface in a west-southwest to east-northeast
direction. The impact velocity is thought to have been about 20
km/s (45,000 mph). The resulting explosion had the power of 1.8
million Hiroshima bombs. The Ries crater impact event is believed
to be the source of moldavite tektites found in Bohemia and Moravia
(Czech Republic). The tektite melt originated from a sand-rich
surface layer and was ejected to distances up to 450 km downrange
of the crater. Stone buildings in Nördlingen contain millions of
tiny diamonds, all less than 0.2 millimeter across. The impact that
caused the Nördlinger Ries crater created an estimating 72,000 tons
of them when it impacted a local graphite deposit. Stone from this
area was quarried and used to build the stone
buildings.
Hint for
English-Speaking-Cachers: The latin Name for Swabia is Suevia
Look here for the
“Swabian Rock” before doing the
Cache:
Wikipedia Nördlinger
Ries Wikipedia Ries
Ereignis
Impact
Database Geopark Ries
Your jobs to log the
Cache:
a) Look for the
“Swabian Rock” at the coordinates. Take a photo (would
be nice:) showing you and the rock.
b) Near the swabian Rock is a
metal stele. There are 3 words at the left side of the stele near
the cache. Send an
email with the 3 words to LATeam.gc@gmail.com. (Subject:
Ries-impact and your gc.com nickname)
c) Declare in your email what
you notice about the landscape when you crossthe
crater-rim.
You don't have to
wait for a log permission.
A visit to the
“Rieskratermuseum”
nearby is recommendet.
|