3.1 b) Mid-latitude Desert Case Study Flashcards
(26 cards)
What is the Colorado plateau?
- centred where Colorado, New Mexico, Utah and Arizona meet in the Four Corners cover 240,000 square miles and ranks as one of the most scenic areas in the world.
- Was created by uplifting
- the region actually consists of a system of massive plateaus separated by faults. Its landforms range from high mountains to fantastically carved canyons
What is a mid latitude desert?
The middle latitudes are found between 30 degrees N/S and 60 degrees N/S
What is the importance of geology in the Colorado plateau?
- Ancient sedimentary rocks, exposed only in the deepest canyons, make up the basement of the Colorado Plateau.
- Igneous rocks injected millions of years later form a marbled network through parts of the Colorado Plateaus’ darker metamorphic basement. These deeply formed rocks were uplifted, eroded, and exposed for eons.
- From these rocks erosion occurred to form a smooth surface where the layers of rock for the Colorado plateau was formed
- Volcanic rocks are also common due to volcanic processes.
- Older rocks are metamorphic and igneous.
- Sediment carried down the floodplain system many years ago were cemented over time to form sedimentary rocks.
What is the importance of relief in the Colorado Plateau?
The Colorado Plateaus starts at about 2,000 feet above sea level, with plateau tops ranging from 5,000 to 7,000 feet and mountaintops reaching nearly 13,000 feet.
What is the importance of water in the Colorado Plateau?
- The Colorado drainage region drains Colorado plateau lands into the Colorado river. One of the main water sources of the Colorado river is the Green river which receives water from mountains outside the area making it an exogenous river
- Has many more drainage basins and flows of water than the Namib
- A rain shadow from the Sierra Nevada means the Colorado plateau receives 6-16 inches of annual precipitation.
- Higher areas receive more precipitation.
- Late summer monsoon season brings storms and flash floods.
Average precipitation of 180mm a year.
What is the importance of climate in the Colorado plateau?
- Due to the region’s generally high altitude, the climate is characterised by cold winters. Summer days are usually hot, but nights are cool; accordingly, the diurnal variation in temperature is considerable. The Colorado plateau is in the northern hemisphere and there is seasonality. It is a semi-arid region, but there are areas that are arid within it.
- The lower the latitude the smaller the seasonal variation- more seasonal variation in Colorado than Namib.
- In Monument Valley in northeast Arizona, precipitation averages just 180mm a year. Temperatures range from an average maximum of 34.4C in July to -3.9C in January. Southeast Utah is part of the Colorado Plateau, a “high desert” region that experiences wide temperature fluctuations, sometimes over 40 degrees in a single day.
- Summer temperatures often exceed 38C, making strenuous exercise difficult. Late summer monsoon season (changing wind direction) brings violent storm cells which often cause flash floods. Winters are cold, with highs averaging -1 to 10 C., and lows averaging -17 to -7C. Though large snowfalls are uncommon (except in nearby mountains), even small amounts of snow or ice can make local trails and roads impassable.
What important landforms are present in the Colorado plateau?
- Orange Hoodoos at Bryce Canyon: Consist of soft rock and hard caprock protecting the softer rock. Range from 1.5-45 metres.
- Coral pink sand dunes- only major dune field in Colorado plateau
- Red cave slot canyon- Utah: Around half a mile long and less than a metre wide.
Monument Valley:
- Plateaus
- Mesas
- Buttes
- Pillars or spires
Interrelationship: The way two or more things are connected and affect one another.
For landforms this could be:
- Sequential development - one landform over time turns into another e.g mesa, buttes, spires.
- Source of material - the erosion of one landform creates a supply of sediment for another e.g. Desert pavements and sand dunes.
What was the formation of the Colorado Plateau?
1)
each sea deposited different types of materiau
that harden to form solid rock-sand became sandstone, mud hardened to Shale. Remains of organisms crushed to limestone. The red colour originates from iron in the rock that is rusting.
2)
* geological disturbance - major uplift. land rose straight up through elevation-forming a high smooth plateau.
* sea was drained backwards.
3)
Colorado river poured into a basin - lake rose and spilled across the plateau-creating a channel through the rock.
4)
* entire grand canyon could have been cut in 6 million years. Lo fossils prove this.
・one of the widest + deepest canyons in the world.
・river ran rapidly-creating incisions.
5)
* extensive lava flavas impacted colorado river L> lava dam’s blocked river completely. Lorising pressure of water behind- dams shatter.
Where is the Colorado Plateau located?
The Colorado Plateau is situated in the southwest USA, between the Rocky Mountains in the north and east and the Great Basin to the south and west.
What is the average elevation of the Colorado Plateau?
The average elevation of the Colorado Plateau is more than 1500 m.
What type of climate does the Colorado Plateau have?
Large parts of the Plateau are classified as a mid-latitude desert.
What is the average annual precipitation at Monument Valley?
At Monument Valley, precipitation averages just 180 mm a year.
What are the temperature extremes in the Colorado Plateau?
Temperatures range from an average maximum of 34.4°C in July to -3.9°C in January.
What is the primary water source for the Colorado River?
The Colorado River derives its water from snowmelt in the Rocky Mountains.
What geomorphic processes shape the Colorado Plateau?
The dominant processes are weathering, mass movement, and fluvial action.
What weathering processes are active in the Colorado Plateau?
Freeze-thaw, salt weathering, and insolation weathering are important, though limited by precipitation.
What types of landslides occur on the Colorado Plateau?
Rockfalls, rockslides, landslides, and slumps occur frequently due to gravitational processes triggered by weathering.
What are the principal desert landforms on the Colorado Plateau?
The principal landforms include pediments, screes, buttes, mesas, and canyons.
What are pediments?
Pediments are extensive gently sloping rock platforms formed from the parallel retreat of mesas and buttes.
How do inselbergs form?
Inselbergs form from the undercutting of weaker shale beds by weathering and lateral erosion by ephemeral streams.
What is the significance of canyons on the Colorado Plateau?
Canyons testify to the power of rivers as erosive agents and the absence of sub-aerial processes in deserts.
What role have tectonic forces played in the Colorado Plateau?
Tectonic forces have uplifted the plateau, allowing rivers to incise their channels and create canyons.
What long-term changes have occurred in the Colorado Plateau?
Long-term changes include the uplift of the Plateau and the dissection of its surface by rivers.
What short-term changes occur in the Colorado Plateau?
Short-term changes include minor rockfalls, sediment transport through wadis, and surface wash across pediments.
