United States or Bhutan ? Vote for the TOP Country of the Week !
Professor Ramsay has published an account of a downthrow in Anglesea of 2,300 feet; and he informs me that he fully believes that there is one in Merionethshire of 12,000 feet; yet in these cases there is nothing on the surface of the land to show such prodigious movements; the pile of rocks on either side of the crack having been smoothly swept away.
The throw of these faults varies from seven hundred feet to more than a mile. The escarpments, however, are due in a large degree to the erosion of weaker rock on the downthrow side. The Highlands of Scotland meet the Lowlands on the south with a bold front of rugged hills along a line of dislocation which runs across the country from sea to sea.
Ramsay has published an account of a downthrow in Anglesea of 2300 feet; and he informs me that he fully believes there is one in Merionethshire of 12,000 feet; yet in these cases there is nothing on the surface to show such prodigious movements; the pile of rocks on the one or other side having been smoothly swept away.
After the upthrown block has been worn down to this level, differential erosion produces fault scarps wherever weak rocks and resistant rocks are brought in contact along the fault plane; and the harder rocks, whether on the upthrow or the downthrow side, emerge in a line of cliffs.
This rock may be made by the consolidation of volcanic cinders, of angular waste at the foot of cliffs, or of fragments of coral torn by the waves from coral reefs, as well as of strata crushed by crustal movements. FAULT SCARPS. A fault of recent date may be marked at surface by a scarp, because the face of the upthrown block has not yet been worn to the level of the downthrow side.
A normal fault with a hade of 15 degrees, the original fault scarp remaining. A normal fault with a hade of 50 degrees, the original fault scarp worn away, showing cliffs caused by harder strata on the downthrow side. A thrust fault with a hade of 30 degrees, showing cliffs due to harder strata outcropping on the downthrow. A thrust fault with a hade of 80 degrees, with surface baseleveled.
Professor Ramsay has published an account of a downthrow in Anglesea of 2300 feet; and he informs me that he fully believes there is one in Merionethshire of 12,000 feet; yet in these cases there is nothing on the surface to show such prodigious movements; the pile of rocks on the one or other side having been smoothly swept away.
The passages I have quoted, with the comments I have ventured to give, make plain the poetic exaggeration of his view, and sufficiently prove why his theory no longer gains any considerable support. To build up a dream-picture of mother-rule on such foundations was, of necessity, to let it perish in the dust of scepticism. But is the downthrow complete? I believe not.
It appears to be a "fault," whose "downthrow," though slight, is clearly indicated by an area of lower ground on the E. There is a great number of small craters in the neighbourhood of this formation.
Word Of The Day