The Student's Handbook of Physical GeologyG. Bell and Sons, 1884 - 514 pages |
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Page 25
... shale . These have been broken off , and blown out by the force of the explosions ; but the greater number of the ejected fragments are pieces of molten rock or lava . The viscid scum which forms on the surface of the rising lava ...
... shale . These have been broken off , and blown out by the force of the explosions ; but the greater number of the ejected fragments are pieces of molten rock or lava . The viscid scum which forms on the surface of the rising lava ...
Page 83
... shale are comparatively imper- vious to water , though their constant wetness shows that they are not absolutely impermeable . Čauses of Springs . - The position of springs is there- fore always determined by the nature and relative ...
... shale are comparatively imper- vious to water , though their constant wetness shows that they are not absolutely impermeable . Čauses of Springs . - The position of springs is there- fore always determined by the nature and relative ...
Page 88
... shale , clay , or peat ; the fissures below are then widened by aqueous solution , till the roof can no longer support itself at certain points , but falls in and pits the surface ; the result is a succession of swallow holes , in which ...
... shale , clay , or peat ; the fissures below are then widened by aqueous solution , till the roof can no longer support itself at certain points , but falls in and pits the surface ; the result is a succession of swallow holes , in which ...
Page 92
... shale has a tendency to slip after heavy rain , as may be seen in many of our railway cuttings . In dry weather the contraction of the clay leads to the formation of inter- nal cracks , and when rain falls the water flows down these ...
... shale has a tendency to slip after heavy rain , as may be seen in many of our railway cuttings . In dry weather the contraction of the clay leads to the formation of inter- nal cracks , and when rain falls the water flows down these ...
Page 101
... shale . Rapidity of Erosion . - From what has already been stated , it will be seen that the erosive power of any stream- i.e. the quantity of material which it can remove from its valley - depends upon four circumstances— 1. The volume ...
... shale . Rapidity of Erosion . - From what has already been stated , it will be seen that the erosive power of any stream- i.e. the quantity of material which it can remove from its valley - depends upon four circumstances— 1. The volume ...
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Common terms and phrases
accumulated acid action alumina amount angles anticlinal augite basalt beds blocks bottom calcareous called carbonate of lime carbonic acid chalk chemical clay cleavage cliffs coal coast colour consist containing coral cracks crystalline crystals denudation deposits depth described detrition distance district dolerite dykes earth earth's crust elevation erosion excavated fault feet felspar fissures Foraminifera formation formed fragments Geol glacier glauconite gradually granite greensand ground hills horizontal hornblende igneous rocks island joints Jukes lake land lava layers less limestone magnesia mass material matter metamorphic metamorphic rocks mica miles mineral mountain observed occur origin Orthoclase outcrops particles pebbles planes porphyritic portion present pressure produced quartz rain reef river salt sand sandstone shales shells shore side siliceous Silurian slope solid solution sometimes stones strata stratified rocks stream structure sulphate surface synclinal thickness tide tion Trans valley vertical volcanic waves