Content Benchmark E.8.C.5
Students know geologic processes account for state and regional topography. E/S
Your family has decided to drive from Las Vegas to Reno, NV to see your mother’s family.
Another dreaded trip, you think. Your ecstatic mom says “This would be a great time to study
the topography of Nevada. You know I did study science in college.” Oh boy, you think to
yourself. What a treat, another long trip down the thruway looking at rocks. Your mother
exclaims, “This trip will be great! I will teach you all about the geological processes of Nevada
along the way! Get packing…”
Nevada is among the most interesting states to study topography and the geologic processes that
act on the crust of the “Silver State.” Without a significant soil cover due to the Mojave Desert’s
climate, it makes it easier to study the geologic processes that make Nevada truly a geologist’s
paradise. With significant extinct volcanoes, plentiful canyons, and magnificent basin and range
geology, Nevada boasts textbook geology that can be studied throughout the state.
Basin and Range Geology
Nevada, located near the western edge of the North American Plate, has experienced significant
tectonic events throughout its history. Among the most visible expressions of this tectonic
activity is the Basin and Range topography that covers most of Nevada and parts of the
Southwestern US. The Basin and Range has been created by the stretching of Earth’s crust,
which has expanded the width of this area by 100%. As this region was stretched, it thinned out
creating large faults. (See fault types below.) With a stretched out crust, normal faults have
created the basin and range topography of the region. In Nevada, the basins and ranges are a
result of normal faults which lie in a northeast – southwest trend. Basins, created by the down
drop fault block, alternate between the ranges throughout the geophysical province. Figure 1a
illustrates that normal faults are the primary cause of the Basin and Range geology of the desert
southwest. The normal fault creates a break and movement in the crust forcing the left portion of
the block upwards, whereas the right hand portion moves downward creating the basin.
Alternative terminology for this type of faulting states that the upward fault block is known as
the horst, and the downward block as the graben. The basin or graben will become a low
elevation area where sediments will deposit creating a moderate elevation area. The northeastsouthwest trend of the mountains and valleys are apparent in a digital elevation map shown in
Figure 2.
Faulting
The solid rigid crust of Earth is broken into many large pieces called plates. Plates shift along the
surface, as a result of plate tectonics, this shifting creates fractures in the crust. Faults are the
result of tectonic forces, specifically, the movement of crust along the fracture.
Faults
Earth’s crust is a rigid layer that fractures and faults creating many different topographic features
such as mountain ranges, valleys and plateaus. Faults are the result of tectonic forces acting on
the earth’s crust. Three main types of faults (Figure 1a-c) are evident on Earth’s surface and are
categorized into three different types based on the processes that create the fault: Normal
(extension), reverse (compression), and strike-slip (horizontal).
Normal Faults
Normal faults are the result of crustal extension or tensional stress. Crustal extension occurs
where the plates are moving away from a certain point, such as a plate boundary. The crust
becomes stretched out, and a fracture develops into a normal fault. The remaining blocks of
crust, known as the footwall (horst) and hanging wall (graben), are a result of the fault movement
along the plane.
Figure1a. A normal fault is a result of crustal extension, or the stretching of Earth’s crust.
(From http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/Study/Images/NormalFault.gif)
Reverse or Thrust Faults
Reverse or thrust faults, are a result of tectonic forces that compress or shrink the crust. Reverse
faulting can happen along plate boundaries or any where tectonic forces push the crustal plates
against each other. This type of faulting causes the hanging wall to slide (up) past the footwall. A
thrust fault is a reverse fault that has a low angle fault plane (close to the horizontal), whereas a
reverse fault has a very high angle fault plane (closer to the vertical).
Figure 1b. A reverse fault is where the hanging wall moves up along the fault plane relative to the footwall block.
(From http://facweb.bhc.edu/academics/science/harwoodr/Geol101/study/Images/ReverseFault.gif)
Strike-Slip Faults
Strike-slip faults are a result of horizontal movement of Earth’s crust. Tectonic forces act on the
crust causing one block of crust to move in the opposite direction of the other block of crust. The
result of these faults is localized earthquakes along the fault plane. The most familiar area in the
world where a strike-slip fault is occurring is the San Andreas Fault in California. Where the
coast of southern California is moving basically northward in comparison to the
inland/continental portion of California, eventually the city of Los Angeles will slide
northwestward and end up near the San Francisco Bay.
Figure 1c. A strike-slip fault is the result of horizontal movement of Earth’s crust
resulting in the offset of two blocks of crust.
(From http://facweb.bhc.edu/academics/science/harwoodr/Geol101/study/Images/StrikeSlipRLFault.gif)
Figure 2. The Basin and Range topography and the north-south trending alternating mountains
and valleys are illustrated in this digital elevation map of Nevada.
(From http://www.seismo.unr.edu/graphics/Maps/nv-topo.jpg)
To learn more about Basin and Range geology and other important physiographic provinces of
North America, go to http://wrgis.wr.usgs.gov/parks/province/basinrange.html
Canyons
Canyons are a prominent geologic feature, particularly in the desert southwest. Canyons are a
deep valley between steep sided cliffs, while most canyons are developed primarily by a river
that erodes through less resistant rock. Weathering acts further upon the canyon to wear down
the walls and widen the canyon, although minimal weathering exists in canyons in the southwest.
Among the more famous canyons of the world is the Grand Canyon, Arizona, which has been
eroded by the Colorado River, mostly over the past 6 million years. Figure 3 represents the
multiple layers of strata that the Colorado River erodes into a v-shape incision.
Figure 3. The Grand Canyon strata have been eroded into a v-shaped river over the past 6 million years by the
Colorado River.
(From http://www.answersingenesis.org/creation/images/v27/i3/canyon_fig2.jpg)
To read more about the Grand Canyon, go to
http://geology.com/articles/age-of-the-grand-canyon.shtml
Alluvial Fans
Alluvial fans are a common landform in Nevada as they are a primary result of flash flooding, or
water erosion in the mountains. Alluvial fans are sediment and debris deposits that form in a fan
shape as floods and gravity carry debris down slope. The distance the material, or alluvium
travels through the canyon and down slope is related to the carrying capacity of the flood water.
If a higher energy flow moves through the canyon, the alluvium will be carried further than if a
lower energy flow moves through the canyon. Also, the higher the energy of the flow, the larger
the size of objects moved will be, slow moving water may only carry pebbles and silt, fast
moving water may move boulders. Figure 4 shows the fan shape of the deposit and subsequent
water channels in the foreground of the picture. In the background of the picture, the canyon
splits the mountain into two portions.
Figure 4. Alluvial fans are a common feature of Nevada, known as one of the most mountainous states in the US.
(From http://lang.sbsun.com/projects/fireflood/graphics/alluvialfan.gif)
To view images of alluvial fans in the United States, see
http://www.uoregon.edu/~millerm/fan.html
To read more about alluvial fans in Death Valley National Park, CA, go to
http://wrgis.wr.usgs.gov/parks/deva/rfan.html
Volcanoes
Volcanoes are an integral part of the geologic history of the state. Figure 5 defines the sites of
major volcanic activity for the state of NV. Most volcanic activity outlined in the map is the
result of extensional forces on the crust resulting in the upwelling of magma. These volcanoes
are quite young, geologically, and they have been active in the Cenozoic Era, from 65 million
years ago to present. The volcanoes of Nevada are mostly cinder cones, or smaller calderas.
Figure 5. A map displaying the major volcanic areas of Nevada. Courtesy of the USGS.
(From http://vulcan.wr.usgs.gov/Volcanoes/Nevada/Maps/map_nevada_volcanics.html)
Volcanoes are an opening or a rupture in the crust of the Earth. These openings are a result of
tectonic forces and are found mostly in convergent and divergent zones of crustal activity.
Volcanoes are classified as being active, dormant, or extinct. An active volcano is one that is
currently erupting or one that is showing signs of erupting. Dormant volcanoes have the potential
to erupt, while extinct volcanoes are unlikely to erupt ever again. Supervolcanoes, like
Yellowstone NP, are the exception of this classification, as they are calderas, which erupt
between long periods of time. The last eruption was approximately 640,000 years ago and
scientist date the caldera at 2 million years old. Caldera formation is illustrated in Figure 7,
where a volcano erupts and the overlying pressure, or weight of rock topples into the center of
the volcano leaving a crater like depression in the volcanic area.
Figure 6. A typical volcano diagram showing major components of an active volcano.
(From http://usscouts.org/bbugle/bb0701/bb0701_files/image045.jpg)
Figure 7. Caldera formation illustrating the collapse of overlying rock.
(From http://www.uwgb.edu/DutchS/GRAPHIC0/ROCKMIN/Ig-Rocks/CALDERA.GIF)
View interesting caldera pictures from around the world, and learn more about caldera
formation, by visiting http://vulcan.wr.usgs.gov/Glossary/Caldera/description_caldera.html
Content Benchmark E.8.C.5
Students know how geologic processes account for state and regional topography. E/S
Common misconceptions associated with this benchmark
1. Students may believe that earthquakes cause volcanic eruptions.
A commonly held misconception among students is that earthquakes cause volcanic
eruptions around the world. Although they are often related, as they are both significant
geological events that produce great change, neither event has been directly linked as a cause
or effect of the other. Often, students will look at a map, particularly looking at the Ring of
Fire in the Pacific Ocean and see that earthquake and volcano locations are close in distance.
Although, the scale of the map may place them very close to each other, they may be
hundreds of miles apart. Secondly, students believe that earthquakes in the crust of Earth will
cause fractures in the crust where mantle magma will rise up, which would actually occur
very infrequently.
Although scientists are unsure of the evidence of the relationship of earthquakes and
volcanoes, you may visit the United States Geological Survey – Volcanic Hazards site to
read more about this important geological activity. Access this information at
http://volcanoes.usgs.gov/Products/FAQs/FAQ_EQ+Volc.html
2. Students incorrectly think that Nevada doesn’t have volcanoes.
Volcanoes are a common geologic feature of topography located near plate boundaries. Not
long ago, geologically speaking, Nevada was located near the active western edge of the
North American plate where fractures and faults in the crust allowed magma to rise up to the
crust and create frequent volcanic activity. This has resulted in volcanoes located in Nevada
which have erupted within the Cenozoic Era, lasting from 65 million years ago to present.
These eruptions have produced volcanic flows of mainly basalt rocks.
Evidence of volcanoes in Nevada are provided in a geological map by the Nevada Bureau of
Mines, located at http://www.nbmg.unr.edu/dox/e30.pdf
3. Students may incorrectly believe that plate tectonics causes topographic features, such
as mountains, to form very quickly.
A commonly held misconception is that students believe that mountains develop very
quickly. Geologically, mountains can develop quickly, in the form of volcanic activity, but
most mountains are created by the folding and faulting of Earth’s crust. Most movement of
Earth’s crust happens at a very slow rate, as geologists’ measure the movement of Earth’s
crust in inches per year. Infrequently, an event will occur, like the 9.0 magnitude earthquake
in the Indian Ocean of 2004, where the crust shifted approximately 20 meters, displacing
ocean water creating a devastating tsunami that took the toll of more than 250,000 lives off
the coast of Northern Sumatra in the Indian Ocean.
Mt. Everest, the result of convergent-convergent plate boundaries, is a mountain that is
continuously increasing in height. Approximately 50 million years ago, the landmasses of
Eurasia and India have collided and have risen up to create the Himalaya Mountains, the
tallest mountain range in the world.
To understand the dynamics of plate tectonics, go to an excellent publication by the USGS at
http://pubs.usgs.gov/gip/dynamic/dynamic.pdf
4. Students incorrectly think that Nevada doesn’t have earthquakes.
Nevada is among the most active states in regards to the number of earthquakes. Due to
Nevada’s proximity to the San Andreas Fault, and numerous faults in the crust of Nevada,
this state ranks among the highest in the number of major earthquakes experienced.
Although, the major cities of Las Vegas and Reno haven’t experienced a large earthquake
(magnitude 5.0 and greater), the state of Nevada experiences many smaller earthquakes.
To learn more about Nevada and earthquakes, the University of Nevada at Reno has an
informative website on earthquakes for over 100 years. See http://www.seismo.unr.edu/.
To view a map of tectonic features and faults in Clark County, NV, go to
http://www.nbmg.unr.edu/dox/b62/B62%20Plates/B62%20PLATE%205.pdf
Content Benchmark E.8.C.5
Students know how geologic processes account for state and regional topography. E/S
Sample Test Questions
1. Which of the following landforms are created by two tectonic plates converging?
a. canyon
b. mountain
c. earthquake
d. river valleys
2. The Basin and Range geology of Nevada and parts of the Southwestern US is the result of
a. crustal stretching
b. crustal shrinking
c. crustal splitting in half
d. crustal compression
Questions 3 and 4 refer to the map located below.
(From http://www.seismo.unr.edu/graphics/Maps/nv-topo.jpg)
3. The Basin and Range of Nevada is shown above. Which of the following landforms are
represented in this map?
a. rivers and valleys
b. valleys and mountains
c. volcanoes and earthquakes
d. valley and earthquakes
4. The orientation or direction of the majority of mountains in Nevada are
a. Northwest – Southeast
b. East – West
c. South – Southwest
d. Northeast – Southwest
Questions 5 and 6 refer to the map below.
(From http://quake.usgs.gov/recenteqs/)
5. Based on the map above, which area has the highest frequency of earthquakes?
a. Northern California
b. Southern Nevada
c. Northern Nevada
d. Southern California
6. A majority of earthquakes occur on the San Andreas Fault line in California. Which
statement is most accurate regarding this active strike-slip fault?
a. two plates are moving away from each other
b. two plates are sliding in the same direction
c. two plates are moving towards each other
d. two plates are sliding past each other in opposite directions
Question 7 refers to the diagram below.
7. In California, the San Andreas Fault is the most famous type of this fault in the world.
What type of fault is causing a horizontal movement along the Earth’s crust?
a. Block fault
b. Normal fault
c. Strike slip fault
d. Reverse fault
Questions 8 and 9 refer to the diagram below.
8. Based on the diagram and your knowledge of geology, what type of fault is a common
feature of the Basin and Range topography of the Southwestern US?
a. Block fault
b. Normal fault
c. Strike slip fault
d. Reverse fault
9. Based on the diagram, what type of movement is the crust experiencing?
a. Extension
b. Convergent
c. Compression
d. Transform
Question 10 refers to the diagram below.
10. Based on your knowledge of the Grand Canyon and landform development, what is the type
of erosion that was MOST responsible for carving the Grand Canyon?
a. wind
b. water
c. gravity
d. ice
Content Benchmark E.8.C.5
Students know how geologic processes account for state and regional topography. E/S
Sample Test Questions Answers
1. (b)
2. (a)
3. (b)
4. (d)
5. (d)
6. (d)
7. (c)
8. (b)
9. (a)
10. (b)
Content Benchmark E.8.C.5
Students know how geologic processes account for state and regional topography. E/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. Volcanoes!
Volcanoes! is an interdisciplinary set of materials for grades 4-8. Through the story of the 1980
eruption of Mount St. Helens, students will answer fundamental questions about volcanoes. The
teaching packet reflects the goals of the National Science Education Standards developed by the
National Research Council and incorporates a number of related subjects, including other
sciences, social studies, language arts, and mathematics.
To access this lesson guide, go to
http://erg.usgs.gov/isb/pubs/teachers-packets/volcanoes/
2. Image Gallery of Landforms
The National Aeronautics and Space Administration (NASA) have provided a comprehensive
guide to landforms in this visual guide. This is a valuable resource to display to students who are
unfamiliar with most landforms in Nevada and outside the area. A link is provided for student
activities to further enhance the lesson.
To visit this website, go to
http://daac.gsfc.nasa.gov/geomorphology/GEO_COMPLETE_TOC.shtml
3. Mojave Desert Landforms
An excellent resource for teachers who want to learn more about the Mojave Desert, this
geological guide provides in-depth research and spectacular pictures. Each chapter of this guide
provides an approachable understanding of the climate and geological processes that shape the
Mojave Desert.
To access this website guide, go to
http://pubs.usgs.gov/of/2004/1007/
4. Hydrology and Landforms
This exciting lesson from the Northeast Ohio Geoscience Teachers and Kent State University
brings hands on activities to the classroom in a clear and informative lesson for grades 3 -12.
Students have the opportunity to examine satellite photos, model wind and water erosion and
recognize local landforms. Facilitators can use this lesson plan over a few days or during a block
period to maximize learning.
To access this lesson plan, go to
http://neogeo.kent.edu/activities/NEOGEO-hydrology%20and%20landforms.pdf
5. Landforms and Topographic Map Assessment
An easy and effective module, it provides students the opportunity to view landforms on
topographic maps. Each slide provides a separate map and feature. At the completion of the
module, students need to match the appropriate map to the landform feature. This module is an
excellent method to review difficult topographic and landform relationships.
To access this website, go to
http://rockyweb.cr.usgs.gov/outreach/topofeaturequiz.pdf