Earth space science 2
What is the rock name of an intermediate rock with two distinct grain sizes?
Andesite porphyry
What is the difference between magma and lava?
Magma is molten rock located below the surface; lava is molten rock erupted above ground.
How can plants physically weather a rock?
Plant roots exert outward pressures as they grow.: As plants grow, their roots thicken. If these roots are in a rock fracture, this can force the rocks apart.
The production of tabular slabs of rocks caused by unloading of material overlying igneous bodies is known as _____.
Sheeting
Which of the choices below is a type of mechanical weathering? Choose all that apply.
Sheeting, frost wedging, root wedging
What coal is soft, black in color, and produces soot upon handling?
bituminous
Which sedimentary rock forms from the compression of swamp material?
coal
Rock salt is an example of a(n) __________, deposited by saturation and precipitation in evaporating water.
evaporite
When lava erupts at Earth's surface, what type of rock is produced?
extrusive: Magma that reaches the surface cools quickly, has fine-grained texture, and produces extrusive rocks.
What agent might metamorphose rocks found adjacent to a large magma body?
hydrothermal solutions
Which of the following best describes why the Vishnu Schist is visible at Earth's surface?
identified the reason why the Vishnu Schist is found at Earth's surface.
_____ igneous rocks are those that cool below the surface.
intrusive: Intrusive igneous rocks form by the cooling and solidification of magma beneath the surface.
Ultramafic rocks contain __________ and are commonly found in __________.
olivine; mantle
What is rock texture?
the way a rock looks
Which of the following is a characteristic of a conglomerate?
A conglomerate is made up of course grains that are poorly sorted.
Which is an example of a sedimentary rock composed of solid masses of intergrown crystals?
Correct! Rock salt is a sedimentary rock that contains intergrown crystals of halite.
Why are mineral bands in metamorphic rocks light and dark colored?
Dark minerals rich in iron and magnesium separate from light minerals rich in silica and aluminum.
Which of the following statements regarding weathering and erosion is NOT true?
Erosion and weathering have the same definition and can be used interchangeably.-The terms weathering and erosion are not the same. Weathering breaks down rock and erosion carries grains away.
Why are garnets used in sandpaper?
Garnets have a value of 8 or 9 on the Mohs Hardness Scale, making them very abrasive.- Garnets are not only beautiful, but useful as well!
How are metamorphic rocks formed?
Preexisting rock is altered through heat and pressure.
By what process did the gabbro turn into amphibolite?
The gabbro was heated to 500 °C and buried a few miles below the Earth's surface.- Heat and pressure are key components to the metamorphic process.
Which of the following is a likely explanation for why there is limestone near the summit of Mount Everest, the tallest mountain on Earth?
The limestone found at the top of Mt Everest was formed in an ocean- Based on your knowledge about limestone, you have correctly identified the conditions under which the limestone formed. Even though it is currently at the top of Mt. Everest, the tallest mountain on Earth, the limestone formed in an ocean before the mountain formed.
In what type of igneous feature would you find rocks with a vesicular texture?
The surface of a lava flow: Because escape of gas from lava is possible only at or close to the surface of Earth, lava flows may possess vesicular texture.
What role does hot ion-rich water play in the process of metamorphism?
Water migrates into host rock carrying ions to stable minerals in order to facilitate growth of new metamorphic minerals.
For a detrital sedimentary rock that contains mudcracks, you could be confident that the environment in which it formed was _____.
alternately wet and dry- Alternating wet and dry conditions would be a prime environment for the formation of mudcracks.
Application of low-grade metamorphic forces to a rock causes _____.
an increase in rock density- Application of low-grade metamorphic forces to a rock causes an increase in rock density.
What is foliation?
banding in metamorphic rocks that results from the reorientation of minerals
Where do most metamorphic rocks form?
between a few and many kilometers beneath Earth's surface-
What sedimentary rock type contains angular cobble-sized clasts?
breccia
The geologic laboratory where you work received a sample for analysis that is composed of calcite that includes many microscopic fossils of marine organisms and reacts with acid. What name would identify this rock?
chalk- Chalk is a biochemical sedimentary rock composed of calcite and contains many microscopic fossils of marine organisms.
Which environment of deposition is NOT represented by the rocks in Capitol Reef National Park?
glacial- None of the sedimentary rock layers in Capitol Reef National Park were deposited during a glacial episode.
What would you call a granite that has undergone metamorphism and now exhibits foliation?
gneiss
Which of the following metamorphic rocks are foliated?
gneiss and slate
What do we call a metamorphic rock that has coarse-grained texture, minimal amounts of mica, and contains minerals that are segregated into bands?
gneiss- A metamorphic rock that fits this description is classified as gneiss.
What kind of metamorphic texture results in the segregation of light and dark mineral bands?
gneissic texture
What property of detrital sedimentary rocks can be indicative of the energy of sediment transport?
grain size- Grain size in a detrital sedimentary rock typically indicates the amount of energy associated with the transport of the sediment. High-energy transport can move much larger grains than low-energy transport.
What element is principally responsible for making olivine, pyroxene, amphibole, and biotite dark?
iron: Iron is common in mafic rocks and minerals; in fact, "mafic" refers to the high iron and magnesium content of these materials.
Abundant plant material accumulating in a swampy environment with __________ is required for peat to form.
low oxygen levels
How is anthracite produced from bituminous coal?
metamorphism
How will minerals orient when a rock is put under shear stress?
parallel to the direction of the shear stress
Name the progression of coal types with increased heat and pressure from burial.
peat, lignite, bituminous, anthracite
How will foliation in continental metamorphic rocks formed during subduction be oriented?
perpendicular to the direction of plate movement
How will minerals grow when a rock is put under normal stress?
perpendicular to the direction of the greatest stress
How will minerals orient when a rock is put under normal stress?
perpendicular to the direction of the greatest stress
Which of the following textures indicates two stages of cooling and crystallization?
porphyritic
Which of the following minerals is most resistant to chemical weathering?
quartz
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: Physical and chemical weathering often works hand-in-hand to break apart rocks.
In your field area you find a quartz sandstone unit with cross-bedding in it that is on the order of 2 m high. In what environment would you deduce this rock formed?
sand dunes- Quartz sandstone with 2-meter-scale cross-bedding would be typical of sand dunes.
Do metamorphic rocks look like the preexisting rock from which they form?
sometimes, but not always
In the list below, indicate in which of the environments fossilization is likely to occur. Note that fossils contain organic matter.
swamp, floodplain, ocean floor
How do metamorphic rocks reach Earth's surface?
through removal of overlying rocks
What does the term aeolian mean?
wind-borne origin
What do we call a metamorphic rock that has a coarse-grained texture, is dominated by mica, and contains no other notable minerals?
mica schist- A metamorphic rock dominated by mica and with a coarse-grained texture is classified as schist.
Which two rock types would you expect to see sitting next to each other after a very long period characterized by only uplift and erosion?
metamorphic and sedimentary rocks
What is salt weathering?
the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart
Consider the ways in which the physical environment (geography) of the outcrop is different from the environment in which the sediments that make up the rocks were deposited 160 to 130 million years ago. Elevation, in geology, refers to the distance an object is above sea level (0 m or 0 ft). The road cut is located in the Canadian Rockies, yet geologists tell us that rocks of the Mist Mountain Formation were deposited near sea level. By checking the elevation of the road cut in Google Earth, determine, approximately, how far above sea level the rocks are now.
1 km (1000 m), or 0.62 mi (3280 ft)- The rocks exposed in this road cut outside Canmore, Alberta, were uplifted from near sea level to their current elevation by the same compressional forces that formed the Canadian Rocky Mountains. The structural features (anticline, syncline, and fault) visible in the outcrop are due to compressional tectonic forces. They are a small-scale version of the much larger structures that were formed by rock deformation as the crust of western North America was shortened (compressed) and uplifted during the Laramide orogeny (mountain building episode), giving rise to what we call the Rocky Mountains between 80 and 55 million years ago.
Which of the following scenarios best describes how sheeting will develop in an igneous rock?
A subterranean pluton is exposed at the surface, releasing confining pressure.: As the pressure lowers, the rock will expand slightly, creating the fractures.
Which two minerals are most common in detrital sedimentary rocks?
Clay minerals are the resistant by-product of chemical weathering and quartz is the most resistant common mineral in Earth's crust. They are common in detrital sedimentary rocks.
There is a saying in geology that "small-scale structures mimic larger-scale structures." The anticline, syncline, and fault that you identified in the outcrop in Part G are pretty small on the scale of geologic structures; however, there is a chance that these geologic features mimic the larger scale structures associated with the formation of the Canadian Rocky Mountains about 80-55 million years ago (Ma). This type of rock deformation (formation of anticlines and synclines) is most commonly associated with which of the following tectonic environments?
Compression
Working in the field, you find a rock that contains rounded fragments that are greater than 2 mm in diameter. What would you call this rock?
Conglomerate is a detrital sedimentary rock that is characterized by rounded fragments that are larger than 2 mm in diameter.
Where else might you expect to find metamorphic rocks like the Vishnu Schist of the Grand Canyon?
Deep beneath Earth's surface, where sedimentary layers have been buried. In a mountain range.
What is a coarse-grained rock composed of intermediate plagioclase feldspar and pyroxene?
Diorite: Diorite is a coarse-grained rock with intermediate plagioclase feldspar and pyroxene.
How does gypsum form?
Gypsum forms from evaporation of shallow seas by a chemical process.
What mineral is the major component of rock salt?
Halite-
Which of the following best describes the difference between differential stress and confining pressure?
In differential stress, the stresses on the sides are greater than the force of gravity. Stresses are the same on all sides for confining pressure.
Examine the images of the Grand Canyon below. Notice that most of the canyon consists of layers of sedimentary rocks, but if you were to hike down into the inner gorge you would encounter the Vishnu Schist, a metamorphic rock. Which of the following processes were involved as the Vishnu Schist metamorphosed?
Intense pressure due to regional metamorphism.- identified the origin of the Vishnu Schist.
What is the most abundant chemical sedimentary rock in Earth's crust?
Limestone is composed of calcite and is the most abundant chemical sedimentary rock in Earth's crust.
Which of the following describes the orientation of the long axes of rocks and mineral grains in relationship to the stress applied?
Mineral grains are oriented parallel to the direction of the weakest stress applied. The long axis of a rock is parallel to the direction of the weakest stress applied.- Both mineral grain orientations and the long axes of rocks are perpendicular to the direction of the greatest stress applied, which is parallel to the direction of the weakest stress applied.
Why do bands of minerals form when rocks are put under normal stress?
Minerals dissolve, atoms migrate to new locations, and minerals reform.
Could metamorphic rocks reach the surface of a planet without rock-uplifting processes?
No, metamorphic rocks must be uplifted and exposed by erosion.
Choose the most likely scenario for how this rock formed. You can infer the environmental conditions where the rock formed from the characteristics of the clasts. For example, in places where sediments are affected by high-energy waves or wind, clasts will be weathered to a similar size and thus will be well sorted. In places with quiet, calm water, small clasts like mud are most likely to accumulate in thin layers.
Rocks eroded from mountains were deposited over a short time in a dry environment, where they were buried by other sediments and cemented into rock.- Understanding the conditions in which this rock formed is important for interpreting the history of geologic events. For example, this conglomerate, called the Leesburg Conglomerate, formed in a low-energy environment where principally limestone fragments mixed with other types of rock during the Triassic.
Why are the sedimentary layers at Capitol Reef tilted?
The Laramide Orogeny is responsible for tipping the strata on their sides.
From what you learned in the video, compare the Pleistocene climate to present-day climate of the western United States.
The Pleistocene was wetter and cooler relative to present-day climate.
Here you will find a dark, thinly bedded layer overlain by a more thickly bedded, tan sandstone layer. Sediments that are deposited rapidly in water commonly have uneven basal (bottom) surfaces, where either the fluid that was transporting the sediments scoured and eroded the underlying deposits, or the weight of the overlying sediments pushed down into and deformed the underlying deposits. These basal sedimentary bedforms provide us with an indication of the relative age and stratigraphic position of the rock units. Now that you've had the opportunity to observe the outcrop in detail, identify the direction in which the sedimentary rocks become younger.
The rock layers to the right (east) of this section of the outcrop are younger than those to the left. These layers were laid down, and then an outside influence forced them into their present orientation.- to the right (east)
Why does quartzite not exhibit foliated texture?
There are very few or no tabular minerals in quartzite.- Foliation doesn't occur in quartzite because there are very few or no tabular minerals in the parent rock.
As a geologist, you always want to first locate your field site by asking the questions, "Where is this outcrop?" and "How might the rocks that I'm looking at fit into the regional geologic picture?" Traditionally, this was done on a map. With modern technology, one can locate the outcrop using a Global Positioning System (GPS) device (if you are in the field) or Google Earth (if you are working remotely on a computer). Accurately locating your field site will help you look for relationships with data from other nearby or regional field sites, and it will help other geologists to locate the same site for future studies. Now, determine where you are (your field site) in the world. Choose the map that best locates your field site.
This location is found in southern Alberta, Canada, near the border of British Columbia. Next, you will determine its orientation.
Contact metamorphism takes place when rocks _____.
come in contact with a magma body-When rocks come in contact with a magma body, they can be altered by contact metamorphism.
Which processes result in mineral flattening during metamorphism?
dissolution followed by crystallization
What is the most efficient agent of metamorphism?
heat
What is the most efficient agent of metamorphism?
heat-Heat is the most efficient agent of metamorphism because it provides the energy to drive reactions.
What is a mantle plume?
hot mantle rock rising from deep within the Earth
At a mid-ocean spreading center, alteration of rocks by chemically active fluids causes metamorphism by __________.
replacement or substitution of ions in the pre-existing rock- Correct Metamorphism of rocks at a mid-ocean spreading center by chemically active fluids causes metamorphism by the replacement or substitution of ions in the pre-existing rocks.
What type of rock will sand become when lithified?
sandstone
In addition to mineralogic composition, the degree of metamorphism in a rock is also characterized by _____.
texture- Texture refers to grain size and is used with mineralogic composition to characterize the degree of metamorphism.
Which of the following processes is most likely responsible for the broken rocks found in the Cathedral Lake, Colorado image?
frost wedging
Metamorphism is driven by heat and pressure. High heat can cause rock minerals to recrystallize in the process of metamorphism. Rocks that are buried deep in Earth are subjected to equal pressure from all directions. This confining pressure can cause a phase chang e but does not fold rocks. On the other hand, pressure from mainly one direction—as is the case of this metamorphic rock and like what happens at a convergent plate boundary—causes differential stress and often leads to folding. Metasomatism is the process in which chemical-rich fluids can metamorphose rock by changing its chemical composition. Most metamorphic rocks have the same chemical composition as their protoliths (the "parent rock," or the original nonmetamorphosed rock from which a metamorphed rock was formed). However, metasomatism actively changes their chemical composition, making it harder to determine the protolith. Return to the Gigapan image. Closely examine the rocks for evidence of metamorphic agents. Determine the metamorphic agent(s), or main metamorphic process(es), of the dark metamorphic rock in the Gigapan image.
Heating and pressure in one main direction- This rock was metamorphosed by a combination of heating and directional stress. This gives the rock its intense metamorphic grade and small-scale folding. If it had been formed by heating due to the injection of the igneous body, its grade would change away from the contact with the lighter igneous rock
Metamorphic textures are defined by the size and shape of the mineral grains that make up the rock as well as the spatial relationships between the grains. The textures can be divided into rocks that are foliated and those that are nonfoliated. Foliated metamorphic rocks show signs that their minerals have been reoriented into layers. Minerals in nonfoliated metamorphic rocks have no orientation. When a rock is metamorphosed and its initial textures remain visible, it is said to have undergone low-grade metamorphism. Rocks whose layering and other characteristic textures have been obliterated have undergone high-grade metamorphism. This Gigapan image shows a dark metamorphic rock in contact with a lighter igneous rock (granite). Review the statements below, and determine which are correct about the dark metamorphic rock on the left in the Gigapan image.
The metamorphic rock has undergone high-grade metamorphism. The metamorphic rock shows foliation This dark metamorphic rock has metamorphosed from a sedimentary rock. It is foliated, shown by the compositional banding, and has experienced high-grade metamorphism, shown by the small-scale folding of those layers. Knowing how to recognize these features is important to geologists in discovering the history of rocks.
Geologists often investigate past environments. The sediments contained within sedimentary rock provide important clues to environment history, namely the environment in which this sediment was deposited. The following outcrop characteristics are helpful in establishing past environments: bedding thickness, composition, and textural features, such as ripples or cross-bedding. For this component, you are asked to make observations of the sedimentary bedding characteristics of the outcrop. Bedding is defined as the arrangement of sedimentary rocks in beds or layers of varying thickness and character, oftentimes separated by bedding planes, which are planar or nearly planar surfaces that visibly separate each successive layer of stratified rock (of the same or different lithology) from the preceding or following layer. Now, based on your observations of the Gigapan outcrop and the following classifications of bedding thickness, estimate what type of bedding best describes the majority of the outcrop? Note that bed thickness is provided in both metric (cm) and US Standard (inch) units of measurement. Use the width of the Hospital (H) sign post visible in the foreground of the Gigapan image as an approximate guide against which to compare the thickness of the sedimentary layers. Let's assume that the sign post is 5 cm (2 inches) wide. While some of the rock layers are thicker than the sign post, many are about the same thickness, or even a little bit thinner. Bed thickness (centimeter) Bed thickness (inch) Bed descriptor 1 to 3 0.4 to 1.2 very thin 3 to 10 1.2 to 4 thin 10 to 30 4 to 12 medium 30 to 100 12 to 40 thick > 100 > 40 very thick
The rock layers in this outcrop are considered "thin" since the majority of them fall between 3 cm and 10 cm (1.2 in. and 4 in.).
The question geologists attempt to answer when they approach an outcrop for the first time is "What kind of rocks are these?" Knowing the rock type helps to put the exposure into a geologic framework, from which additional questions can be asked, and answers determined. Now that you've had an opportunity to examine the Gigapan image "up close," identify the type of rock present in the outcrop.
The rocks in this outcrop are sedimentary rocks that are exposed in a west-facing road cut along Three Sisters Drive in Canmore, Alberta. Canmore is a gateway town to the Canadian Rockies that is located along the Trans-Canada Highway about 60 miles (100 km) west of Calgary.-Sedimentary
Rock units tell us about Earth's past, so if we find evidence of geologic processes that have directional components (e.g., sedimentary bedding, igneous dikes, folds, faults, direction of plate movement, etc.), we need to be able to accurately reconstruct those directions. Also, in terms of the scientific method, it helps other geologists to be able to recreate a field investigation step-by-step to confirm or refute any previous findings. In the physical world, geologists would use a compass to orient themselves with respect to the outcrop, as well as determine the orientation of stratigraphic and structural features. In the virtual world, you will take advantage of the fact that all images in Google Earth are ortho- and georectified, meaning that the scale of the images is consistent and that the spatial orientation of the image is correct with respect to the true cardinal directions (i.e., north, east, south, and west). Choose the most accurate representation of the outcrop's orientation and your vantage point (where you [or the photographer] are standing in relation to the outcrop).
We are standing on the side of the road facing east while looking at this road cut. Reflect on why it's important for geologists to be specific about outcrop orientation and to record this information accurately in a field notebook or on a tablet computer.- circle at west
When fine-grained tabular minerals in a rock at depth are subjected to differential stresses, they _________.
align perpendicularly to the plane in which the maximum compressive stress is applied- When differential stresses are applied to rocks that contain fine-grained tabular minerals, they cause the minerals to align perpendicularly to the direction in which the greatest stresses are applied, as space in the rock is reduced.
In addition to temperature, which of the following agents increases with depth in Earth?
pressure- Pressure on rock increases with depth and, along with temperature, is influential in metamorphism.
Which structure is common in sedimentary rock?
ripple marks, mud cracks, cross-bedding, fossils- Fossils, cross-bedding, ripple marks, and mudcracks are all features found in sedimentary depositional environments.
What do we call a metamorphic rock that has microscopic to very fine-grained texture, breaks into slabs or sheets and is dull on the surface?
slate- A metamorphic rock that has very fine-grained texture and slaty cleavage would be identified as slate.
In the United States, the most common type of coal is __________ and the largest producing state is __________.
sub-bituminous; Wyoming
Which of the following describes a texture containing bubble-shaped cavities?
vesicular
The formation of sedimentary rock requires _____.
weathering and erosion of pre-existing rocks-Weathering breaks down pre-existing rock into particles, while erosion moves the particles to a site of deposition. These processes begin the formation of sedimentary rock.
Which of the following agents is capable of moving sediment from the site of formation to the site of deposition?
All of the answers are correct.-Sediment can be moved by wind, running water, ice, or waves.
What changes are occurring in the igneous pluton that would result in sheeting?
volume increase: With a reduction of confining pressure, the pluton expands.
What material was added to powdered rock during Tuttle and Bowen's experiments?
water
How does water content of granitic magmas change as the magmas move towards Earth's surface?
water content decreases
Which of the placemarks in the Exfoliation Dome folder is the best example of an exfoliation dome?
A
What is an accessory mineral?
A mineral that makes up a relatively small portion of the total rock composition
Which of the following statements about the rock cycle is correct?
A sedimentary rock subjected to intense heat and pressure will become a metamorphic rock.
What do freeze-thaw and salt weathering have in common?
Both freeze-thaw and salt weathering require rain and force rocks apart physically.
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.: Chemical weathering does its work on the surface of the rock. The more surface there is, the more weathering that can take place.
The chemical weathering process known as dissolution is most effective in the breakdown of which of the following minerals?
Calcite: Calcite is soluble in water and dissolves, especially if the water is slightly acidic.
Which of the following agents move sediment from one place to another?
Glaciers, wind, rivers.
Which of the following best describes the difference between granite and rhyolite?
Granite is phaneritic and rhyolite is aphanitic.
What are the two most important driving forces of metamorphism?
High heat and pressure
What is one way a glassy texture forms?
Lava cools rapidly.
There are four main types of mechanical weathering: frost wedging in which rocks are broken by water freezing within cracks, salt crystal growth in which rocks are broken by salt freezing within cracks, sheeting in which rocks dome upward and peel off, and biological activity in which living things such as tree roots break rocks apart. You will visually identify these types. Note that one of the images is not an example of mechanical weathering.
Limestone cave is a weathering process not related to the physical breakdown of rock.
What is the definition of physical weathering?
Mechanical processes break substances into smaller pieces.: All physical weathering does is break rocks and minerals apart. Nothing more is needed.
An igneous rock becomes buried, is subject to high heat and pressure, and recrystallizes. This rock then is eroded, transported, deposited and subsequently lithified. Which rock types—in order—did the original igneous rock develop into?
Metamorphic and sedimentary
Which of the following igneous rocks contains no mineral crystals?
Obsidian: Obsidian cools so quickly that the individual ions in the lava do not have time to organize into a crystalline structure.
Which of the following minerals would be the first to crystallize in a cooling magma?
Olivine
The progressive nucleation of minerals from the melt leaves the magma depleted in certain elements. This change in magma composition is called magmatic differentiation and accounts for the great variety of igneous rocks found in nature. The separation of liquid and solid phases through crystal settling further contributes to this diversity. Use your understanding of Bowen's reaction series and crystal settling to determine which of the following mineral associations should not be found in nature.
Olivine, potassium feldspar, quartz
Which of the following textures describes an igneous rock with anomalously large crystals?
Pegmatitic
Metamorphic rocks can form when which of the following conditions are met?
Pre-existing rocks undergo metamorphism when they are subjected to heat and pressure without melting: Applying high heat and pressure to any type of rock causes metamorphism.
Sand dunes are typically dominated by quartz grains and very little other mineral matter. Why does this selection occur?
Quartz is extremely resistant to all forms of chemical weathering.: Quartz is not affected by hydrolysis, oxidation, or dissolution because it is an extremely resistant mineral.
Which of the following statements about rock melting is most accurate?
Rock can remain solid, become partially melted, or melt completely at the same depth within Earth, depending on the temperature.
The formation of sedimentary rocks occurs under what conditions?
Sedimentary rocks form when weathered particles are cemented and/or compacted.
Which of the following rock types is most abundant on Earth's land surface?
Sedimentary rocks: You have successfully completed the exercises on the rock cycle. You should now have a better understanding of the different processes that are involved in the creation and destruction of rocks.
What do pumice and scoria have in common?
The both exhibit a vesicular texture.
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.
The minerals in granite rocks chemically weather into other minerals, known as products. Just as these minerals within granite, an intrusive igneous rock, crystallized from magma at different temperatures, they also have different resistance to chemical weathering. Minerals like quartz, which crystallize at low temperature, are less susceptible to chemical weathering than minerals like feldspar, which crystallize at high temperatures.
As a geologist, you always want to first locate your field site on a map. It helps other geologists to locate the field site for future studies and helps you look for relationships with data from nearby field sites. Determine where you are (your field site) in the world. Choose the map that best locates your field site.
The outcrop is located in the northeast corner of Minnesota. Take a moment to reflect on what you know about this area already. Is it an active plate boundary? Does it have mountains, volcanoes, glaciers, etc?
ock units tell us about Earth's past. If we find evidence of geologic processes that have directional components (direction of plate movement, folds and faults, mineral foliation, wind and water currents, etc.), we need to be able to accurately reconstruct those directions. In terms of the scientific method, documenting outcrop orientation helps other geologists recreate the field investigation step-by-step to confirm or refute previous findings and associated interpretations. Choose the most accurate representation of the outcrop's orientation given your vantage point (as viewed using the Gigapan in relation to the outcrop).
The photographer/image is looking towards the west. In other words, the outcrop faces east at the lake behind the photographer. Reflect on why it's important for a geologist to be specific about outcrop orientation and to record it accurately in a field notebook. If you don't recall why, reread the introduction to this question. Circle pointed at the east
Which of the following statements provides the best description of the chemical weathering seen in the Newspaper Rock photo?
The rock face has desert varnish.
What does an igneous rock with a pyroclastic texture tell a geologist?
The rock was likely formed by a violent volcanic eruption.
Which of the following is the best example of biological weathering evident in the Lassen NP image?
The trees that are wedging their roots into joints in the rocks.
Which of the following is not an example of biological weathering evident in the Snake River image?
The water interacting with the minerals in the rock.
Most igneous rocks never reach the surface. However, igneous rocks other than those formed in volcanoes are found exposed on many parts of Earth. How do you account for this phenomenon?
They formed at depth and have been exposed by uplift and erosion.
During the late Cretaceous, the Bisti Badlands were home to numerous animals including turtles, crocodiles, and even dinosaurs. What type of environment were they living in?
They were living along rivers and deltas on the edge of an inland sea.-
Why is Tuttle and Bowen's experiment useful to geologists?
This experiment allows geologists to interpret where granitic rock solidifies beneath Earth's surface.
How does water content of melt change with increasing pressure?
Water content increases with increasing pressure.
How can the creation of ice result in physical weathering?
Water expands in volume when freezing, exerting pressure on a container.: Water expands in volume when solidifying, which pushes outward on a container.
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.
How did weathering destroy New Hampshire's Old Man in the Mountain?
Water migrated along fractures in the rock, where it froze and wedged the rock apart.: Ice wedging took advantage of pre-existing fractures in order to destroy the landmark.
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:
Choose the cross-section sketch that best represents the rock units you observe at this scale.
You have come to see that there are two main rock units stacked on one another. Next you will interpret the type of environment where this rock formed. Understanding the rock unit features in an outcrop can be important in order to develop some interpretation for how it formed. Next you will interpret the type of environment where this rock formed. Red rock bottom and black on top
While working in the field, you discover an outcrop of metamorphic rocks. What can you conclude from this observation?
You know that these rocks formed at great depth below the surface: Metamorphism requires significant amounts of heat and pressure. Where would this take place?
Which of the following is an example of chemical weathering?
a car fender getting rusty: The iron in the steel body of the car is bonding with oxygen to produce rust.
A geologist sends you a sample that was collected in the field. You find that it is a gray-colored igneous rock containing amphibole and intermediate plagioclase feldspar. Using Bowen's Reaction Series as a guide, how would you describe its composition?
andesitic: Amphibole and intermediate plagioclase feldspar occur in the andesitic temperature regime.
Pyroclastic debris from a volcanic eruption can include _____.
ash, cinders: Along with bombs and lapilli, ash and cinders are common components of pyroclastic debris ejected from volcanoes.
What is the term used to describe a very large, widespread, and deep intrusive body of igneous rock?
batholith: A deep, large-sized igneous intrusion fits the description of a batholith.
What are the two important processes involved in lithification of sedimentary rocks?
cementation and compaction
Which of the following climates would have the greatest degree of ice wedging?
cold in the winter, warm in the summer, and with moderate precipitation: Cold temperatures are necessary to create ice, but the water would flow into the fracture in the warm weather.
What is the classification of igneous rocks based on?
composition and texture: Composition is determined by the minerals in the rock and texture relates to the grain size. This is the basis of the classification of igneous rocks.
What process forms igneous rocks?
cooling and solidification of magma: Igneous rocks form from the cooling and solidification of magma, or molten rock. Magma is also known as lava when it is present on the earth's surface.
Which natural processes act as metamorphic agents?
differential stress from mountain building
A hoodoo with a cap rock of sandstone and shale below is an example of __________.
differential weathering-
Which of the following processes of mechanical weathering is most likely responsible for the appearance of Half Dome?
exfoliation
Considering the following list, which is not an example of chemical weathering?
exfoliation: Exfoliation is the breakdown of rocks by removal of overburden, a physical process.
During hydrolysis, ions and clay minerals are produced by the decomposition of which of the following Earth materials?
feldspars: Exposure of feldspar to water causes it to break down by hydrolysis into clay minerals and ions.
Working in the field, you see a thin, dark-colored igneous sill across the valley. Without seeing the sill up close, what texture would you expect it to possess?
fine grained: Because rock is a relatively poor conductor of heat, smaller intrusions would tend to cool more quickly than large intrusions.
In temperate and polar regions, the accumulation of talus slopes at the base of steep, rocky cliffs is most often attributed to which of the following processes?
frost wedging: Where steep, rocky slopes are subjected to many freeze-thaw cycles, talus slopes can accumulate at the base.
Which of the following rocks would most likely experience sheeting?
granite: Granite forms from magma cooling in subterranean magma chambers.
An igneous rock that contains quartz and potassium feldspar would have a mineralogic content placing it in the range of __________.
granitic or felsic rocks: Granitic rocks are associated with quartz and potassium feldspar.
Why does magma have a tendency to rise after its formation?
it is less dense than the surrounding rock: As rock melts, the density decreases. This process causes the magma to rise.
Which of the following surface openings are best represented by the parallel features seen at the Openings for Weathering placemark?
joints
As a result of partial melting, magma originates in __________.
mantle and crust: Tectonic forces act in the mantle and crust to cause rocks to melt and form magma.
Which of the following processes would best explain the green patina seen on the Statue of Liberty?
oxidation
Of the following processes, which is not an example of mechanical weathering?
oxidation: Right! Oxidation is a process whereby rocks are altered by a chemical change (reaction with oxygen in water or air).
Use your understanding of Bowen's reaction series to determine which of the rocks below will crystallize the fastest. The chemical composition of the rocks is:
peridodite
When sheeting develops in an igneous pluton, fractures will develop in an orientation __________ to the direction of expansion.
perpendicular -This effect makes layers separate from the pluton like layers of an onion.
Basalt is an igneous rock that can be identified by its small crystals. What are they composed of?
pyroxene and calcium-rich plagioclase feldspar: Basalt is a mafic fine-grained igneous rock that contains pyroxene and calcium-rich plagioclase feldspar.
Basaltic igneous rocks contain which of the following minerals:
pyroxene and calcium-rich plagioclase feldspar: Pyroxene and calcium-rich plagioclase feldspars reflect a basaltic composition.
The chemical weathering process known as oxidation would be most effective in the breakdown of which of the following Earth materials?
pyroxenes: Minerals such as pyroxene that contain iron are very susceptible to oxidation.
Which one of the following is NOT an example of a mechanical weathering process?
reactions that occur when rain mixes with carbon dioxide to form carbonic acid-The formation of acid promotes chemical weathering.
What is a fine-grained igneous rock composed primarily of very small crystals of potassium feldspar and a few large crystals of quartz?
rhyolite porphyry: This rock is of a felsic (rhyolitic) composition with a porphyritic texture.
Most igneous rocks are primarily composed of:
silicate minerals: Silicate minerals are the most common minerals in Earth's crust and therefore make up the bulk of most igneous rocks, though minerals from many other important groups may also be present.
What experiments did Tuttle and Bowen perform?
tests of the temperature and pressure conditions required to melt granite and form magma
Pre-existing rocks are broken down into smaller particles by which of the following processes?
unloading,thermal expansion,frost wedging
