chapter 6 & 7
What is a delta?
A delta is a triangular landform created where a stream enters a body of water and deposits sediment.
Compaction/lithification
A dump truck dumps a load of gravel on your lawn. The dirt below it becomes more consolidated
What do freeze-thaw and salt weathering have in common?
Both freeze-thaw and salt weathering require rain and force rocks apart physically.
Match the sediment size with the appropriate rock.
Breccia − Gravel Arkose − Sand Quartz sandstone − Sand− Sand Siltstone − Silt Claystone − Clay
___ weathering alters the internal structure of rock materials.
Chemical
What sedimentary structure is present in this photo?
Cross-bedding
Sediment Erosion/transport
Dirt being blown off a patio The dirt going down the drain after you give your dog a bath and drain the tub
Deposition of sediment
Dust collecting on furniture
Consider the marked locations in the figure below. Rank these locations based on rates of weathering as a function of climate. NOTE: Moisture is more important than temperature.
Fastest ~ Slowest A C B
Rank the rocks from fastest weathering to slowest weathering.
Fastest ~ Slowest Peridotite, Gabbro, Diorite, Granite
With the addition of water, the minerals in granite rocks chemically weather into other minerals, known as products. Test your knowledge of the by-product of each mineral as a result of chemical weathering by labeling the minerals below with their respective products.
Feldspar: Clay Quarts: No change Olivine: Limonite
What sedimentary structure(s) can you identify in the above image?
Ripplemarks
Why are sedimentary rocks important?
Sedimentary rocks provide geologists with information necessary to study the history of Earth and also hold various resources of economic importance.
Compaction will be the most significant lithification process for which of the following rocks?
Shale
Rank the rocks in order of the rate of chemical weathering they would experience, assuming they are all located in the same warm wet climate.
Slowest ~ Fastest Granite with few or no cracks Granite with abundant cracks Basalt with few or now cracks Basalt with abundant vesibles
How does physical weathering cause chemical weathering to be more effective?
When a rock is physically broken into smaller pieces, there is more surface area on which chemical weathering can occur.
Which are two most common minerals in detrital rocks?
quartz and feldspar
How is anthracite produced from bituminous coal?
metamorphism
You will sort each example into its category of chemical weathering process.
Hydrolysis: -Feldspar in granite rocks weathering to clay Oxidation: -Red color of rocks in Arches National Park -Yellow-stained rocks that used to contain pyrite before it is weathered Dissolution: -the salty taste of ocean water -caves formed in limestone
Weathering of rock
Ice expanding in a crack in the road creating a pothole Tree roots extending into a rock layer and breaking it down
Frost wedging
Image of ice on mountians showing clone-shape rock piles/talus slope beneath
Which is the most abundant chemical sedimentary rock?
Limestone
Read the following descriptions of several different environments. Based on the information given, sort each environment into the correct bin for an environment that would experience predominantly mechanical weathering or predominantly chemical weathering.
Mechanical weathering would predominate: -A cold dry environment experiencing uplift, in which material is being removed by erosion from an underlying pluton/intrusive igneous rock. -A cold wet environment at high elevation, in which freezing and thawing is common. Chemical weathering would predominate: -A hot environment with many short but intense rainstorms. -A hot humid climate with heavy precipitation that occurs all year. -A warm wet environment with above average yearly rainfall and several stormy seasons each year.
What is diagenesis?
The textural, compositional, and other changes that occur to sediments after deposition
What does the presence of mudcracks indicate about the paleoenvironment?
There was a wet environment that is drying up.
Why does water frozen in the cracks of a rock help to break down the rock?
Water expands when frozen and physically forces the rock apart.
The fissures formed as a result of ___ in exfoliation domes can be further enlarged by ___ in areas subjected to seasonal freeze-thaw cycles.
sheeting frost wedging
In the United States, the most common type of coal is __________ and the largest producing state is __________.
sub-bituminous; Wyoming
What is salt weathering?
the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart
Which of the three images in Figure 2 would be most susceptible to chemical weathering and why?
C: Physical weathering has created more surface area for chemical weathering to attack.
Potassium feldspar weathers in the presence of water containing ___
Carbonic Acid
Match the chemical weathering process with the correct definition.
Dissolution − minerals dissolved in acidic water. Oxidation − positive ions lose electrons to oxygen. Hydrolysis − positive ions are replaced with H + or O H −.
What are the two basic categories of weathering?
mechanical and chemical
Match the mechanical weathering process with the correct definition.
Frost wedging − expansion of ice forces a rock apart. Salt crystal growth − mineral crystal development forces a rock apart. − mineral crystal development forces a rock apart. Sheeting − reduction of pressure on a pluton results in concentric layers breaking off. Biological activity − living materials break down a rock.
What is the definition of physical weathering?
Mechanical processes break substances into smaller pieces.
Which of the following is an example of chemical weathering?
a car fender getting rusty
Which of the following defines depositional environment?
an area where sediment was deposited under certain conditions in Earth's past
Other than sand dunes in a desert environment, where else would you expect to find well-rounded and sorted sand deposits?
beach
The break down of rock by moving fresh materials to the surface by burrowing animals is an example of mechanical weathering due to ___
biological activity
What coal is soft, black in color, and produces soot upon handling?
bituminous
A greenhouse gas called ___ influences the rate of chemical weathering.
carbon dioxide
___ has a crucial influence on the rates of all types of mechanical weathering.
climate
Which of the following correlate to transport distance?
grain size and rounding
sheeting
image of exfoliation dome at Yosemite
salt crystal growth
image of rocky sea shore
biological activity
image of tree root growing into a rock fracture
not an example of mechanical weathering
limestone cave with freshwater
Abundant plant material accumulating in a swampy environment with __________ is required for peat to form.
low oxygen levels
A conglomerate is poorly sorted with well-rounded grains. This rock was likely formed in what depositional environment?
mountain stream
What sedimentary structure is visible in this image?
mudcracks
Iron weathers through the process of ___
oxidation
Name the progression of coal types with increased heat and pressure from burial.
peat, lignite, bituminous, anthracite
Using the picture of the Entrada Sandstone in Figure 1, try to identify the evidence of physical and/or chemical weathering present.
rusty color and fracturing
___ can contribute to crumbling roadways in areas where salt is spread to melt ice and snow in winter.
salt crystal growth
Describe the distribution of sedimentary deposits you would expect to find on a delta.
sand in channels, mud on floodplain
If all the particles in a detrital sedimentary rock are nearly the same size, it is
very well-sorted
Wind-blown sand deposits would most likely be __________ and __________
very well-sorted; well-rounded
A smooth grain shaped like a cigar is __________ and shows ________
well-rounded; low sphericity