FOUR GEOLOGY QUESTIONS!!!!! REALLY NEED HELP!!!!!!

[Lauffer32]

1. How can you distinguish a sill from a buried lava flow?
2. how are batholiths emplaced?
3. What criteria are used to classify plutons?
4. why are volcanoes associated with highly viscous magmas more explosive than volcanoes associated with fluid basaltic magmas?

DONT HAVE TO ANSWER ALL. EVEN IF YOU CAN ANSWER SOME THAT WOULD BE GREAT

[Clanad]

From my dog-eared copy of Field Geology comes this:
1. A flow is often vesicular or scoriaceous in its upper portion and often has pores and brecciated structures near its base. On the contrary, a sill is usually free of visible pores; but sometimes there are numerous short apophyses extending into the superjacent strata and these, when viewed in cross-section, may make the upper surface of the sill look as if it were scoriaceous lava. The cavities and depressions of a buried lava flow are generally filled with sediments that have their bedding lamination parallel to the main stratification above. Flows are not uncommonly overlaid by sediments that contain angular blocks or water-worn pebbles of the lava. Eroded fragments of the sill can not be present in the superjacent beds which were invaded by the sill. Study of this case would show that the seeming fragments of sill will have chilled margins and that the enclosing rock has a metamorphic aureole around each fragment... Inclusions of the superjacent beds may be found in the sills but never in flows...

(Contd.)

[Clanad]

(Contd.)

2. Geologists generally agree (at least here in the western U.S.) that batholiths were emplaced by foreceful injection as the magma moved upward. This injection resulted in the forcefull shouldering aside and deforming the country rock... The depth at which this occurs may also result in "stoping"... a process in which rising magma detaches and engulfs pieces of country rock...

3. For intrusive, plutonic and usually phaneritic igneous rocks where all minerals are visible at least via microscope, the mineralogy is used to classify the rock. This usually occurs on ternary diagrams, where the relative proportions of three minerals are used to classify the rock.

(Contd.)

[Clanad]

(Contd.)

4. If the liquid part of the magma has a high viscosity, then the gas will not be able to expand very easily, and thus, pressure will build up inside of the gas bubble(s). When this magma reaches the surface, the gas bubbles will have a high pressure inside, which will cause them to burst explosively on reaching atmospheric pressure. This will cause an explosive volcanic eruption.

Years since I earned a degree in Geology with specialty of Rocky Mountain foundations and development at a first rate school here in the western U.S.... Best of luck. (Be sure to undertand the relattionship of the terms pluton and and batholiths seen here: http://www.pitt.edu/~...eBodies/1Plutons.html ...)