The mechanical force exerted by running water in undermining cliffs, and rounding off the angles of hard rock, is mainly due to the intermixture of foreign ingredients.
If a hard rock is met with, it is first triturated by an iron rod, and the materials being thus reduced to small fragments or powder, are readily extracted.
The areas of softer rock would be brought low, and the outcrops of hard rock (Plate XV) would constitute ridges during the later stages of an erosion cycle.
The Upper and Lower narrows of the Baraboo (Plate IV) are good examples of the effect of hard rock on the widening of a valley.
Whilst sinking in hard rock, it has ordinarily been the custom to place iron curbs, or cribs, wherever a bed of stone appeared to form a natural barrier between two distinct feeders of water.
Graded reaches in soft rock alternate with steeper declivities in hard rock, forming rapids such as, for example, a stretch of ten miles where the fall averages twenty-one feet to the mile.
How does this fact affect its erosive power on hard rock?
We may infer from this instance how slight is the erosive power of clear water on hard rock.
Lakes having outlets are drained away as their basin rims are cut down by the outflowing streams,--a slow process where the rim is of hard rock, but a rapid one where it is of soft material such as glacial drift.
Grandis, Grattoni, and Sommeiller, for the more rapid tunnelling through hard rock, and with a view to its employment in driving the proposed shaft through the Alps.
As the crevice enlarges and deepens, the stream acquires velocity, and begins to use the bits of hard rock in boring.
It is true that in a torrent we have the same conditions of motion; but there the banks are either of hard rock or, if of detritus, they are continually moving into the stream in the manner before described.
On the Tibetan plateau, on the other hand, most of the ranges are distinguished by their rounded outlines and soft consistency, and their striking poverty in hard rock, which in the best cases only crops out near the summits.
I didn't think you could get an explosive that would successfully shatter that hard rock, but you seem to have done it.
Many holes had been drilled in the face of the cliff of hard rock, and the charges tamped in.
That used for my giant cannon would merely crumble thehard rock for a short distance.
That is what is bothering me now--the unexpected strata of hard rock we have met with, which seems impossible to blast.
The above list will hopefully provide you with a few useful examples demonstrating the appropriate usage of "hard rock" in a variety of sentences. We hope that you will now be able to make sentences using this group of words.
