IGNEOUS PROCESSES Flashcards
Which of the following is considered a warning sign of imminent eruption?
earthquake activity
Obsidian is classified as having a __________ texture.
glassy
Which type of volcano erupts with the most force?
composite
Which of the following describes an elongated crack that may serve as a conduit for lava to erupt on the surface?
Fissure
Earthquakes can tell us a lot about the possibility of an eruption. If there are too few earthquakes ________.
it may mean the magma has stopped moving implying it is about to give way.
Most hotspots are ________.
basaltic
Magma may cool and crystallize to become solid igneous rock
very slowly (in centuries to a million years) when it forms a deep pluton.
Why does magma tend to rise upward once it forms?
The magma is less dense than the surrounding rock.
A moving, glowing, descending cloud of hot gases and volcanic pieces
is called a pyroclastic flow or nuée ardente.
Which of the following is not a characteristic of pyroclastic flow?
They move very slow and are not dangerous.
Which describes the melting that takes place when deep hot rock rises to shallower depths without cooling?
Decompression melting
Which type of volcano is the largest but not necessarily the most eruptive?
shield
Which eruption or volcano type is likely to produce the most violently ejected pyroclastic fragments?
Stratovolcano
Pyroclastic flow can be composed of all but which of the following?
water
A sill runs ________ to the surrounding rock.
parallel
The image below (immediately to the right of the person’s head) is an example of a small __________.
dike
The difference between magma and lava is that __________.
magma is found beneath the surface, whereas lava is found at the surface
Granite, a course-grained, felsic intrusive igneous rock is most similar in mineral composition to __________, which is a fine-grained, felsic extrusive equivalent.
rhyolite
In the figure provided below, what type of igneous intrusion is the horizontal rock unit indicated by the arrow?
sill
Which of the following is not a way in which geologists can monitor a volcano with the goal of making short-term predictions about volcanic activity?
radioisotope dating
Which of the following is not considered a type of pyroclastic debris?
pahoehoe
Magma tends to __________.
move upward, away from where it formed
Which type of magma has the greatest silica content?
felsic
Bubbles trapped in lava after the molten material are cooled are called __________.
vesicles
Ash, and larger fragments of pumice are all examples of __________.
pyroclastic debris
An irregular-shaped and bloblike igneous rock body that cooled beneath the surface of Earth is a __________.
pluton
Columnar jointing forms primarily because of __________
Contraction and cracking of rock during the cooling process
Compared with coarse-grained igneous rocks, fine-grained igneous rocks __________.
cool and solidify more quickly
Decompression melting occurs at both __________ and __________.
mid-ocean ridges; hotspots
All things equal, a magma will have __________ viscosity than a lava.
lower
__________ form from piles of pyroclastic debris (mainly lapilli) that fountain out of a vent during an effusive eruption.
Cinder cones
Despite the fact that the temperatures within Earth are hot enough to melt rock, Earth is mostly solid. Why do the rocks within Earth NOT melt?
The pressure is too high.
A batholith is a(n) __________.
large compound igneous intrusion
The interior of Earth consists almost entirely of __________ rock.
solid
Viscosity controls how __________.
fast a fluid flows
