h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hi Shagbark

I've read this entry (tried to find it in Peer Review as you say in the threads below but it was nowhere to be found).

It covers quite an ambitious subject in a short piece but does this quite well. However, when I started to think about how it could be improved, I had a few ideas about reordering the text for improved readability and ended up with quite substantial changes. I've added a few other details after doing a bit of surfing too. I won't blame you if you decide to go with your version (you did write it, after all) but here's what I came up with:

The Sedgwick Geological Trail can be found off the A684 [note to Shagbark: UKanians usually do not refer to these roads as 'Highways' but 'A roads'] near Sedbergh, Yorkshire, England.

It shows a real-life example, one which you can see and touch, of a geological feature known as a 'fault'. A fault, as defined by the US Geological Survey [note to Shagbark: amend the footnote to 'USGS Glossary of Terms', and include the publication date] is

"a fracture along which blocks of crust on either side have moved relative to one another parallel to the fracture."

In other words, the Earth's crust has been locally subjected to intense pressure to a point where it has broken. If the force is sufficient, the 2 broken halves may not only break but also slide past each other.

The build up of pressure in the Earth's crust is largely due to a phenomenon known as 'Plate Tectonics'. Until the 20th Century, the prevailing opinion amongst geologists was that the Earth's crust was like the shell on an egg - a continuous casing surrounding a liquid/semi-solid mass held inside. This idea was challenged with the concept of 'Continental Drift' put forward by a German guy called Alfred Wegener in 1924 but it wasn't until the latter half of the 20th century that geologists accepted and refined this idea further.

Now, the Earth's crust is thought of not as a continuous shell but as a series of interconnected plates, which fit together like a disasterously-made and hopelessly-assembled jigsaw puzzle on a massive scale. Worse, the puzzle pieces (plates) move in 3 dimensions and even worse, they grow and shrink continuously!

So where does the Sedgwick Geological Trail fit into all this? Well, associated with the ongoing process of plate tectonics is the generation of massive pressure, resulting, in some places in the development of faulting.

[Note to Shagbark: I've left out the bit about 'pastures of Yorkshire' as I can't substantiate the reference to 2 plates coming together specifically in that area - my regional geology is rusty and it's better to be sure of your facts and write less than to write something which might be wrong (or at least not entirely accurate).]

The Sedgwick Geological Trail is sited on the Dent Fault and follows the river Clough. Over thousands of years, the river has eroded into the rock, creating outcrops (areas where the rock is visible). The surfaces exposed in the outcrops clearly show the structure and composition of the rock, which changes dramatically as it crosses the fault. To the West of the fault lies a block of strata which are Silurian (approx. 439 Million years in age), whilst to the East, the rock is Carboniferous (approx. 362 Million years old). The relative displacement of one block of rock to the other may be as much as 2.5 km. (Okay, this is peanuts on a global scale but to humans, it's damned impressive).

During what some have called the golden age of geology in Britain, Adam Sedgwick, after whom the trail is named, recognised, mapped and interpreted the fault in this location. Sedgwick went on to become a renowned geologist at Cambridge University and was cited by his contemporary, Charles Darwin in the classic text, 'The Origin of Species'

>>> link to Darwin/Origin of Species - h2g2 should allow this because it's a BBC Online Site - you'll need to GuideML it in though>>>>
http://www.bbc.co.uk/education/darwin/origin/index.htm

Rock Hounds [Note to Shagbark - I prefer the term 'Geologists', whether amateur or professional] come to the trail to see the exposed rock [note to Shagbark: I've left out the bit about the syncline to reduce the size of this entry a little - it's growing.] An abrupt change in the rock type can be seen where the fault cuts the exposure. The chief rock types which can be seen on the trail are limestone (often white and fairly smooth in appearance, when eroded by water), shale (a fine-grained rock, built up of tiny plates of sediment, typically dark in colour) and conglomerate (composed of gravel, pebble or cobble-sized stones, stuck together with a finer-grained material in between).

[Note to Shagbark - I've combined 'Location' with 'To find the trail' and added some specifics...]

Location

Map reference: GR 695 912
Sheet Reference: Sheet 98 in O.S. 1:50 000 Landranger Series

Park along A684 in a gravel car park at the top of a hill. Walk the finished path which leads to the right downhill. At the river, before crossing the footbridge, turn left onto the grass. Now you are on the Sedgewick Geological Trail. The trail is a barely marked footpath, made in the 1980's, in a sheep pasture called Longstone Common. When walking the trail, watch your step because of the presence of sheep, doing what sheep do.

Weatherbeaten wooden posts are numbered with points on the trail. Not all of them are easy to spot. What is easy to see is the river and the strata of the rock on it's other shore. Upon close inspection you can tell where you have crossed the fault, because the nature of the rock along the river changes. At the end of the trail it is a steep climb back to the car park. A guide leaflet about the trail can be bought locally.

Note to Shagbark:
h2g2, now part of BBC Online, is always keen to promote links to BBC Online web pages - here's one to the BBC's GCSE (UK examinations) revision pages - the diagrams are simple but pretty clear. See what you think.
http://www.bbc.co.uk/education/gcsebitesize/science_chemistry/geology/

Hope this all helps
Chin chin
Spitfire

I wish you had sent this three months ago. Orcus and I had a
lengthy dialoge on this.
I think I will put your map coordinates and
bbc link in the footnotes and leave the rest the same.

Hi guys - this may all be a bit late I'm afraid as the article will have long ago winged its way to a sub-editor.
Still, you never know they might read this stuff

You may be right but i noticed they still have it listed in
what's coming up.

Looks like I spoke to soon. The what's coming up page
changed since yeaterday. I hope the editor has my correct e-mail
address. If he uses the one I had as hickory it will come back to him as undeliverable.

I think the sub-eds do look at the conversations attached to the entry so you may be OK.

Yeah, we do. I've just received this article in my latest batch - gimme some time to read it over and I'll probably be back here again asking questions and generally being irritating.