Geology Test 2
Imagine a new and previously unknown sedimentary structure is discovered in a deposit of sedimentary rock. What would be the best approach to try and understand it?
Find a similar structure in a modern environment
Clastic sedimentary rocks are defined and named basely on ____________, while chemical sedimentary rocks are defined mainly on their ____________.
Grain size, composition
The principle of original horizontality states that sediments accumulate in essentially _________. The implication is that tilted sedimentary layers observed today must have been subjected to _________.
Horizontal layers, tectonic forces
How do chemical and mechanical weathering work together?
Mechanical weathering creates surfaces for chemical weathering to take place
volcanic hazard arising from a collapsing eruption column that runs downhill at high speeds. These are associated with explosive eruptions and a mix of lava lapilli, pumice, ash, and hot gases.
Pyroclastic flow
Which of the following is NOT a characteristic of an actively erupting volcano?
Totally covered in a fresh blanket of clean, white snow
Which of the following are ways that viscosity affects gasses in magma?
Viscous magma prevents gas from escaping easily.
What is the difference between weathering and erosion?
Weathering describes how rocks breakdown to smaller pieces, while erosion is the physical removal of those pieces to another location
Which of these is relatively recent volcanic eruptions formed a caldera?
Yellowstone
Which of the sedimentary basins shown here form by stretching and thinning of the continental crust?
a
what type of tectonic event formed the main structures in the Valley and Ridge Province of the Appalachian Mountains
a continental collision
Which of the following factors indicates a high risk for volcanic mudflows or lahars?
a volcano with a thick covering of snow or ice
which of the following is most likely to occur at shallow crustal levels
brittle deformation
which types of eruptions is among the most deadly of natural disasters?
caldera-forming
Huge circular depressions from which volcanoes erupt are called
calderas
What is the sedimentary structure shown in this picture?
cross bedding
when a rock is subjected to tectonic forces and experiences stress that is not the same in all directions, it is under
differential stress
how does gypsum form?
evaporation of water in a lake or sea
compared to non-fractured rocks, the rate of weathering in fractured rocks of the same composition is
faster
how does the silica content affect the behavior of magma?
higher silica makes the magma more viscous
the effect of transportation on a pebbles particle size is best summarized by which statement
its size decreases
what type of eruption is shown in this photograph?
lava dome
sedimentary clasts are
loose fragments of rocks and minerals
lithifies can be defined as
loose sediment hardens into sedimentary rock
earthquakes at Mount St. Helens prior to the major eruption in 1980 were caused by
magma rising in the volcano
Water getting into fractures and freezing, expanding the fracture is an example of what?
mechanical weathering
what type of rock forms through solid-state alteration of a previously existing rock, by heating, pressure, and/or fluid chemistry
metamorphic
which of the following is NOT involved in turning some sediment into sedimentary rock
metamorphism
What indicates changing water conditions, from wet to try?
mud cracks
This relatively small volcanic feature consists of solidified lava and some volcanic ash. What kind of volcano is it?
none of these (scoria cone, caldera, shield, composite)
sedimentary rocks are comprised of material that comes primarily from
other locations
which of the following processes is NOT considered physical weathering
oxidation
the two main processes by which sediment is produced are
physical and chemical weathering
What type of volcano eruption is shown in this photograph?
pyroclastic column
which of the following materials is NOT produced by erupting volcanoes
sandstone
clastic sedimentary rocks are classified primarily on the basis of
sediment size
which of the following rocks is composed of the smallest sedimentary clasts?
shale
What kind of volcano is generally the largest?
shield volcano
the largest type of volcano is called a ____ volcano and is characterized by broad, low angle flanks, a small vent or groups of vents at the top, and basaltic magma
shield volcano
What is the most likely cause of detrital sediment with highly rounded grains?
shorter time since weathering
which of the following characteristics are NOT used to classify and name clastic sediments
the climate in which the clasts are produced
Comparing these two photographs, which eruption has lower viscosity magma?
the fluid cascade of lava
fluvial refers to
the processes and sediment of streams and rivers
what happens to the majority of sediment being carried by moving water as it enters a standing body of water?
the sediment gradually settles to the bottom
what is the main difference between conglomerate and breccia
the shape of the clasts
which of the following processes is NOT considered to be chemical weathering
thermal expansion
which of the following is NOT evidence of recent activity at a volcano?
thick, well developed soil
What is NOT a characteristic of an actively erupting volcano?
totally covered in a fresh blanket of clean, white snow
downslope marine flows comprised of mixed masses of sand, mud, and water are called
turbidity currents
