30 Questions
What type of lava has a smooth, billowy, undulating, or ropy surface?
Pahoehoe Flow
Where are pillow lavas commonly found?
Mid-Atlantic Ridge and Juan de Fuca Ridge
What is the surface expression of an impact structure called?
Impact Crater
What are planar deformation features (PDFs) in minerals within in situ lithologies?
Optically recognizable microscopic features
What are shatter cones?
Distinctive cone or fan-shaped features in rocks
What are high-pressure mineral polymorphs within in situ lithologies?
Distinctive cone or fan-shaped features in rocks
What is a conformable contact in sedimentary rocks?
A surface contact where a sediment layer is deposited over any preexisting rock, the contact is parallel and continuous, representing a continuous time gap.
Define unconformable contact in geology.
Represents a gap or missing information in the geologic record, caused by external processes such as tectonic or erosional processes.
What is an angular unconformity and how is it characterized?
It is the contact between inclined beds and horizontal beds where relatively flat younger strata overlay steeply dipping older strata.
Explain a nonconformity in geology.
It is the contact between sedimentary or volcanic rocks overlying older igneous or metamorphic rock, which may represent a time gap of over one billion years.
What is a disconformity and how are the separated layers oriented?
A disconformity is the contact between two sedimentary rocks that have undergone erosion, and the separated layers are horizontal to each other.
How is a nonconformity different from an angular unconformity?
A nonconformity involves the contact between younger sedimentary/volcanic rocks and older igneous/metamorphic rocks, while an angular unconformity involves inclined beds over horizontal beds.
What is the distinguishing characteristic of a Flute Cast?
Bulbous nose that flares out toward the other end
What causes the formation of Crescent obstacle scours?
Current scour around small obstacles like pebbles or shells
What distinguishes Load Casts from Flute Casts?
Load Casts lack the regular form and orientation of Flute Casts
How are Mudcracks formed and where are they commonly seen?
Mudcracks form due to changes in weather patterns and are commonly seen in palayan (rice fields)
What is the difference between Mudcracks and Syneresis cracks?
Syneresis cracks tend to be discontinuous and vary in shape from polygonal to spindleshaped or sinuous
What is the distinguishing characteristic of a Current Crescent?
Narrow semicircular or horseshoe-shaped troughs around small obstacles
What is the definition of Planar Attitude?
Orientation of two nonparallel lines in a plane
How is Strike defined?
Azimuth of the horizontal line in a dipping plane or the intersection between a given plane and the horizontal surface
What is True Dip?
A dip angle at 90° to the strike
What is Apparent Dip?
Any angle between the plane and the horizontal that is not measured perpendicular to the strike
How is Trend defined?
Azimuth of the horizontal line in a dipping plane or the intersection between a given plane and the horizontal surface
Explain the Right-Hand Rule in the context of strike and dip.
Imagine grasping a strike/dip map symbol with the right hand, palm down, and fingers pointing in the direction of the dip. The thumb then indicates the strike direction to be recorded.
What is the difference between a stock and a batholith based on their surface exposure?
Stock has a surface exposure of less than 100 square kilometers, while a batholith has a surface exposure larger than 100 square kilometers.
Describe the shape of a laccolith and how it forms.
A laccolith has a domelike structure, formed by splitting apart two strata.
What distinguishes a lopolith in terms of shape and concordance with the intruded strata?
Lopolith is lenticular in shape with a depressed central region, concordant with the intruded strata.
Explain the specific location where a phacolith typically occurs and its shape.
A phacolith typically occurs at the crest of an anticline or the trough of a syncline, and it is lens-shaped.
What is the defining feature of an aa flow in terms of its surface characteristics and composition?
An aa flow is characterized by a rough or rubbly surface composed of broken lava blocks called clinker.
How do lobate lava flows differ from pahoehoe flows and where are they commonly found?
Lobate lava flows resemble pahoehoe flows but are more inflated-looking, and they are common on fast-spreading mid-ocean ridges like the East Pacific Rise.
Test your knowledge on different types of igneous intrusions including stock, batholith, laccolith, and lopolith. Learn about their characteristics, sizes, and formations.
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