- | Page
EOSC 221 FINAL QUESTION AND ANSWERS
VERIFIED TO PASS
Question :Chilled Margin
Correct answer:Region of reduced grain size formed due to
rapid chilling of magma against cool country rock, water or air
Question :Country rock
Correct answer:Existing older rock into which an igneous body
intrudes
Question :Xenoliths
Correct answer:inclusions of deep wall rocks or country rocks in
an igneous intrusion
Question :Discordant body
Correct answer:contacts not parallel to any layering in country
rock
Question :Concordant body
Correct answer:contacts parallel to any layering in country rock
- | Page
Question :laccoliths
Correct answer:mushroom-shaped intrusions. Range in diameter
from 1-8 km. Max thickness of 1 km.
Question :Lopolith
Correct answer:a large, lenticular, centrally sunken mass of
igneous rock whose surfaces are concordant with the enclosing rocks. Funnel shaped.
Question :Igneous layering
Correct answer:dense crystals form in magma and 'rain' to floor
of chamber, accumulating in layers
Question :Stock
Correct answer:small discordant pluton with outcrop area of less
than 100 km^2
Question :Batholith
Correct answer:discordant pluton with outcrop area of more than
100 km^2
- | Page
Question :effusive eruption
Correct answer:relatively gentle, non-explosive volcanic
eruption
Question :Explosive eruption
Correct answer:an eruption that is thick and sticky, has a high
gas content, and is high in silica
Question :shield volcano
Correct answer:a wide, gently sloping mountain made of layers
of basaltic lava and formed by quiet eruptions
Question :cinder cone volcano
Correct answer:A small, steeply sloped volcano that forms from
moderately explosive eruptions of pyroclastic material/fragments.
Question :composite volcano
Correct answer:A tall, cone-shaped mountain in which layers of
lava alternate with layers of ash and other volcanic materials.Larger than cinder cone.
- | Page
Question :Volcanic bombs
Correct answer:large blobs of magma that harden in the air
Question :Pillows
Correct answer:lobate forms of lava formed in underwater
eruptions
Question :Columnar joints
Correct answer:elongate polygons formed as a result of
contraction of igneous rocks during cooling. Indicative of rapid cooling. Grows perpendicular to the plane of cooling.
Question :Rock-forming minerals
Correct answer:The common minerals that make up most of the
rocks of Earth's crust. Found in classification triangles.
Question :accessory minerals
Correct answer:Minerals found in lower abundances, rock
classification does not depend on them