Tuesday, 13 January 2003
Monthly Meeting of the Essex Rock & Mineral Society
Small Bodies of the Solar System by Jerry Workman
Notes: R Coleman
It is rewarding to know that you can trust people like Newton & Kepler, because Jerry returned as predicted for another talk about what's going on in our Solar System! He discussed: Asteroids; the Oort Cloud and Kuiper Belt; the difference between meteors and meteorites, stony ones, iron ones, and Meteorites from Mars; Comets; small moons circling the Gas Giants; and impact structures such as small craters, large craters, & ring craters. The quote of the evening was; "You can't see much surface detail of Pluto as it is 2300km across and 4 billion km away from Earth!"
One topic that was raised was the Martian meteorites. The comparison of the gas trapped in a meteorite, said to have come from Mars as another body crashed into the planet and accelerated this piece beyond escape velocity for its journey to Earth, was said to be the same as the present day Martian atmosphere. This is an often quoted "clincher" for the origin of these meteorites. (However, to me, it doesn't seem reasonable that an impact on Mars with an energy release equivalent to a formidable nuclear explosion would result in a gas bubble of the same composition as that of a present day Martian Atmosphere. Which piece of data came first, I don't know (yet) but I suggest you look for where the money is, or to be kind, how the data is explained! It may be more to do with the ratio of isotopic abundance of an element within the gas than the composition. Plus aren't all these rocks of igneous origin? Which begs the question. "What was the Martian atmosphere when these were molten? RC)
Jerry's talk was accompanied by truly fantastic pictures, many of which came from the numerous space missions. In his talk he mentioned that lots of these pictures can be seen on the NASA website. A site which we have referred to in the past. So rather than reiterate endlessly, try the following links and enjoy!
There are some wonderful pictures to be found and I would suggest you search for yourself as the fancy takes. The above links contain many others. You can quite easily spend an evening or two (weeks) going through them. My favourites are images taken from Shuttle Missions and Satellites of the Earth's surface.
My apology for not detailing Jerry's talk in depth, but for those without access to the Internet it did achieve the goal of bringing one up to date. An extremely interesting and well presented talk on an immensely diverse and complex subject. Jerry's expertise certainly shone through during question time.
Announcements
At the meeting we at last had the opportunity to present the Jim Greenwood award to Alan Smart in recognition of his commitment to helping organize the Society's display's at various events over the last few years.
He has quietly gone about; building display cases, cajoling members for the loan of their prized specimens for display, and manned the table, fending numerous questions from the public without any fuzz! The object of this Society is to promote interest in Geology, and displays at public events is an important opportunity not to be missed. Well done Alan for the enthusiasm and interest you have shown in this area and many thanks!
Member's finds on display:
Trilobite:
................................. found by Jon Deith on last year's trip
to Gilwern. The specimen is about 6 to 7 cm long and is complete and quite
large for this location. Most specimens found are of thorax and/or tail.
There is some suggestion that this is the preservation of the exoskeleton
which is said to be shed several times as the trilobite grows. This site
has a peculiarity that the size of specimens found is graded from one
end to the other. Perhaps suggesting the accumulation to be a result of
gentle current/wave action.
The club is planning a return visit later this year to this classic site!
(Please note: In the picture above the colours are false, and were used to enhance the image. Usually it is just a buff coloured rock).
Shark
Tooth
Carcharodon megaladon
(Derived Miocene)
The Naze, Walton, Essex.
Found late last year (2002) by Ursula Deith. Note the polished patina, this is an effect caused by the Red Crag deposit and is natural.
Fossil
Whale ear bone from the Naze, Walton, Essex.
Found by Ursula on the same trip! (How does she do it?)
None of these are common finds for Naze, in fact it is comparable to finding something as rare as "Rocking Horse Droppings"
Shark
tooth, Carcharodon megaladon
Derived Miocene,
The Naze, Walton, Essex (2002)
Ursula wasn't satisfied and went back a week or so later and found another. A smaller tooth but still a size!
And, as you may have guessed, another whale ear bone!
(I give up!)
Something
different, a modern shore crab on its way to becoming fossilized.
Found by Jeff Saward at Seasalter, Kent. Estimates of age vary, amongst those in the know, from a few hundred to maybe 10,000 years. Jeff reckons a couple of thousand. He also says that the matrix is not too consolidated and crumbles away easy when preparing specimens
Lobster
Hoploparia gammaroides.
London Clay
Steeple, Essex.
Found by Jeff Saward
A classic example of this lobster!
Another
find from Steeple, Essex by Jeff Saward
A worked flint tool about 5cm in length! Obviously, lapidary has been around for a long time. No doubt about the origins of this, you can see how the edges have been nibbled. This doesn't happen in nature. It had a lovely feel!
Printing optimized for A4 paper with bottom
margin set to 20mm and all others to 10mm
All pictures & text © R Coleman 24 January 2003