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78 Cards in this Set
- Front
- Back
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Subduction
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Compression - when two tectonic plates collide. Denser plate slides under lighter continental plate and melts into the asthenosphere.
Creates volcanic arcs when -- plate forces magma towards the surface. Formed Cascade and Andes Mtns. |
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Spreading (extension)
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Pulling apart of tectonic plates
Usually when oceanic plates are separating - sometimes continental plates. Creates mid-oceanic ridges when sea floor separates and lava spills out, creating underwater mountain ridges. Continental plates create "rift valleys" -East African Ridge Valley |
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Transverse (strike-slip)
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Two fault blocks slide past one another
Also occurs with plate boundaries -San Andreas Fault- |
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San Andreas Fault
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A continental transform fault that runs a length of roughly 800 miles through California. The fault's motion is right-lateral strike-slip (horizontal motion). It forms the tectonic boundary between the Pacific Plate and the North American Plate.
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Lahars
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Large mudflows caused by melting snow and ice, initiated by large volcanic eruptions.
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How much of the world's water is freshwater?
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3% - Less than 1% is surface and ground water.
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Aquicludes
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Layers of impermeable rock
Often create the beds of aquifers |
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Aquifer
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Ground water stored in soil and porous bedrock
Often found in thick layers of sediment and sand |
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Perched Water Tables
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Small aquifers situated above the main water table
Can be created in Aquicludes |
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Artesian wells
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Ground water under hydrostatic pressure which is forced to the surface
Forms below the elevation where water is fed into the aquifer Creates fresh water springs |
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Cone of Depression
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Occurs at the water table surrounding well drops
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Karst Landscape (topography)
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Sink holes formed over caverns
As sink holes get larger caverns are opened to the surface Valleys form as cavern ceilings collapse Columns of the cavern walls are left as pillars on the landscape |
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Why is water the most erosive force in the desert?
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Little vegetation to hold back erosion
Vegetation helps slow erosion by reducing the friction of water on the soil |
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Arroyos
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Gullies formed in the desert by water erosion
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Alluvial fans
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Large fan shaped features extending from the mouths of canyons consisting of gravel, sand, and silt
Formed by aggredation mud flows caused by intense rains and lack of vegetation to hold back erosion. Mud flows exit the mountain canyons to the desert valley. |
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Playa
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Typically flat and dry center of desert valleys.
During heavy rains, is filled with water and formed a small lake. |
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Salt Flat
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Occurs after a water in a playa sinks into the ground and salt is drawn to the surface.
Often covered in mud |
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Splash Erosion
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Erosion caused by the process of water droplets displacing the soil due to the impact of the droplet.
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What is the impact of splash erosion on the landscape?
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Movement of particles shifts the soil, causing it to become more compacted
Overland flow becomes more intense due to lack of infiltration Soil erosion becomes more intense |
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Lithosphere
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Outer most layer of the Earth
Brittle, ridged rock Continental and oceanic crust |
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Asthenosphere
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Beneath the lithosphere
Made of soft “plastic-like” rock Temperatures are high (2600° F) |
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Stratovolcanoes (composite cones)
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Large conic volcanoes typically existing near subduction zones
Very explosive eruptions due to highly viscous magma; prevents flow of magma and gasses Mt. St. Helens, Mt. Hood, Mt. Rainier - all in the Cascades |
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Calderas
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Central depression in the cone produced by large eruptions of Stratovolcanoes
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Mount Mazama
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A destroyed stratovolcano in the Oregon part of the Cascade Volcanic Arc and the Cascade Range.
The volcano's collapsed caldera holds Crater Lake, and the entire mountain is located within Crater Lake National Park. Most famous for a catastrophic volcanic eruption that occurred around 5,677 (± 150) BC. The eruption, estimated to have been 42 times more powerful than Mount St. Helens' 1980 blast. |
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Mount Rainier
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An active stratovolcano in Pierce County, Washington.
It is the highest peak in the Cascade Range and Cascade Volcanic Arc at 14,411 feet. |
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Shield Volcanos
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Low sloping volcanoes with less explosive eruptions
Broad and Large (Mouna Kea in HI is larger than Mt. Rainier) Magmatic chemical make-up is less viscous so lava pours out of the volcano smoothly |
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"Hot Spots"
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Where shield volcanoes often occur.
Areas where the crust is thin and a magma chamber is close to the surface |
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Cinder Cones
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Small volcanoes that are created by the opening of a narrow vent
High pressure magma is forced to the surface Lava “sprays” out and builds up into a small cone shaped volcano Wizard Island |
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Wizard Island
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A volcanic cinder cone which forms an island at the west end of Crater Lake in Crater Lake National Park, Oregon.
Created after Mount Mazama erupted violently forming the caldera which now contains Crater Lake. |
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Yellowstone
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Situated over a hot spot.
Very explosive Volcanic Caldera (supervolcano) Erupts approximately every 600,000 years |
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Faults
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Fissures in the Earth’s crust that form due to unequal stress
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Normal fault
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Results in a steep cliff as two fault blocks pull away from each other
Typically occur in parallel groups |
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Reverse fault
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Occurs when two fault blocks push together
Crustal shortening occurs |
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Overthrust fault
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Low-angle reverse fault; a large long portion of the crust
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Horst
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Uplifted block in a normal fault that results in a mountain range
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Graben
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Lower fault block that results in a valley.
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Base level
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The level at which there is zero slope
Streams tend toward flattening the landscape through erosion Every stream is trying to reach it Localized - where a river empties into a lake Ultimate - sea level |
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Meanders
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Curved river channel of mature rivers
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Undercut bank (cut bank)
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Stream flow undercuts the bank of one side of the channel
Most intense flow occurs at this point |
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Point bars
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Opposite of the undercut, the flow of the river is much slower
Slow flow leads to sediment dropping out and depositing creating a _____ ___ |
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Meander cutoff
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Increased undercutting of banks leads to widening of the river valley
Eventually, meanders touch and erode land between resulting in a _______ ______ |
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Oxbow lake
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The meander opposite the cutoff - isolated and contains water.
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Valley widening
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Caused by increased undercutting of banks
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Entrenched meanders
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Rapid uplift of the landscape causes the slope of the river to increase leading to rapid down cutting
Meanders are then left incised in the bedrock |
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Natural Bridge
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Forms if a solid layer of rock exists above the point of a meander cutoff.
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Damns
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significant source of electricity
They do not pollute No greenhouse gasses, no nuclear waste |
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Where do glaciers usually form?
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Form in high elevation and high latitude areas with proper climatic conditions.
Must be cold enough to snow and summers are cold enough that snow does not melt away completely. Snow builds up year after year Snow transforms to ice and starts moving downhill |
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Cirques
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Large bowl shaped areas of alpine regions
Easily collect snow Where Mountain Glaciers form |
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Glacier
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A mass of ice which moves down hill due to gravitational pull
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How are glaciers formed?
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Created through the process of snow compaction and densification over time
Snow -> Granular Snow -> Firn-> Glacier Ice |
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Firn
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Thick granular snow, especially on the upper part of a glacier, where it has not yet been compressed into ice.
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Ice Crystal Alignment
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Ice crystals are in the shape of a hexagon
Snow falls in a jumbled pattern - As the snow compacts and becomes more dense, the snow turns to ice and the crystals align Allows for the crystals to slide past each other causing the glacier to flow |
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Ablation zones
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Areas in which the snow from the previous winter has melted off the glacier
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Accumulation zones
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Areas where the snow from the previous winter still exists on the glacier
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Equilibrium Line Altitude (ELA)
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The line dividing the ablation and accumulation zones
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Glacial abrasion
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Glacial ice plucks rock, boulders, and sand, and scrapes along the bedrock
Erodes the land similarly to sand paper on wood |
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Striations
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Scours in the rock created by glacial abrasion
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Crescentic gouges
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Half moon shapes gouges
Formed as a glacially carried rock (on the bed of the glacier) pries loose a piece of bedrock |
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Glacial till
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Unstratified mixture of rock fragment
Silt, sand, gravel, boulders, clay, etc. Deposited directly from the ice |
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Moraines
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Large rock and soil debris piles built up by the “bulldozing” and abrasion of glacial bed load
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Terminal moraine
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A long ridge of glacial debris found at the terminus (or front) of the glacier
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Lateral moraine
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A long ridge of glacial debris found along the sides of the glacier
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Medial moraine
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A long ridge of glacial debris found along the center of the glacier where two glaciers came together, combining their lateral moraines
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Kettle ponds
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Large ponds formed in flat plains
Large blocks of ice broken off from ice sheet are buried Ice melts leaving water in the depression Minnesota’s lakes are mostly these |
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Horns
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Mountain peaks that were carved out on at least three sides (by glacial abrasion)
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Arete
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A sharp edged valley wall carved out by two glaciers on both sides of the wall
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Alpine glaciers
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Glaciers found in mountainous regions
High elevation allows for cooler conditions Snow stays around all year and after many years of snow build up, a glacier forms |
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Nuntaks
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Mountains surrounded by ice
Found in icefields |
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Icefield
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A contiguous grouping of glaciers with a common source area
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Tarns
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Small mountain lakes found in cirque basins
Form after the glacier melts out of the valley |
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Outwash plain
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Large open plain of glacially deposited material
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Eskers
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Long ridges of sediment built up from old entra glacial streams
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Drumlins
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Rounded hills of glacial till created by glacial “bulldozing”
Egg shaped with the narrower end pointing down glacier Likely created as the build up of till puts pressure on the glacier, causing the glacier to lift up and override the till |
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Hanging valleys
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Valleys connecting to the glacial trough which enter the trough at a higher elevation
Smaller tributary glaciers created them |
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U-shaped valleys
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Valleys carved by glaciers are left with a “U” shape (valleys carved by rivers have a “V” shape)
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Glacial trough
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Large “U” shaped valley; often times the main glacial valley
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Laurentide Ice sheet
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North America centered over Hudson Bay
A massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, between c. 95,000 and c. 20,000 years before the present day. Its southern margin included the modern sites of New York City and Chicago, and then followed quite precisely the present course of the Missouri River up to the northern slopes of the Cypress Hills, beyond which it merged with the Cordilleran Ice Sheet. The ice coverage extended approximately as far south as 38 degrees latitude in the mid-continent |
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Little Ice Age
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Cool period in Earth’s history
1400 A.D. to 1900 A.D. Drastically affected societies and history around the world Crops failed in Europe Chinese exploration stopped due to need of wood for heating Glaciers bulldozed farms and small communities in the Alps Reduced Sun energy output is the likely cause |
