Climate Influence on Ice Sheets

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Questions and Answers

What does paleoclimatology study?

The effects of tectonic movements on climate

Past climate change (correct)

Future climate predictions

Current climate patterns

How does the location of continental crust influence ice sheet formation?

By minimizing glacier movement

By increasing ocean currents

By providing an anchor point for ice sheets (correct)

By capturing more snowfall during winter

Which factor contributes to the growth of ice sheets during colder seasons?

Decreased temperatures (correct)

Increased evaporation

Increased rainfall

Higher levels of humidity

What was the global temperature compared to today during the Last Glacial Maximum?

$6^{ ext{o}} C$ cooler Signup and view all the answers

What can significantly increase the size of the ablation zone?

Increasing temperatures Signup and view all the answers

What happens when precipitation falls as rain over ice sheets?

It does not contribute to accumulation Signup and view all the answers

What was the atmospheric CO2 concentration during the Last Interglacial – Eemian period?

~290 ppm Signup and view all the answers

Which of the following is NOT a factor that influences ice sheet growth?

Ocean salinity levels Signup and view all the answers

What prevents adequate drainage in periglacial environments, leading to wet, saturated soils?

Permafrost Signup and view all the answers

Which statement accurately distinguishes between continuous and discontinuous permafrost?

Continuous permafrost has frozen soil everywhere in the area. Signup and view all the answers

What is a pingo, and how does it form?

A mound formed by the freezing of a water lens under the soil. Signup and view all the answers

What primarily drives glacial-interglacial cycles?

Milankovitch cycles Signup and view all the answers

What is the main factor that causes ice sheet ablation?

Subsurface melting Signup and view all the answers

Where are continuous permafrost regions primarily located?

Higher latitudes and elevations Signup and view all the answers

What is the primary factor that drives snow and ice loss in the ablation zone during summer?

Higher summer temperatures Signup and view all the answers

What role does the ice-albedo feedback play in glacial-interglacial periods?

It increases glaciation as ice reflects sunlight. Signup and view all the answers

What is the equilibrium line in relation to ice sheets and glaciers?

The point where accumulation equals ablation Signup and view all the answers

Which of the following is a characteristic of the Midwest Ice Age fauna?

Presence of large mammals adapted to cold environments Signup and view all the answers

Which of the following describes positive feedback in the context of climate change?

A process that enhances the original effect Signup and view all the answers

How does iron fertilization affect CO2 levels in the atmosphere?

It stimulates phytoplankton growth which draws down CO2 Signup and view all the answers

What is a consequence of colder water in the context of CO2 solubility?

It enhances CO2 drawdown from the atmosphere Signup and view all the answers

Which cycle is responsible for glacial-interglacial transitions and energy changes from the Sun?

Milankovitch cycle Signup and view all the answers

What is the effect of increased dust on oceanic phytoplankton growth?

Enhances nutrient delivery to oceans Signup and view all the answers

Which factor is NOT directly related to ice sheet growth?

Meltwater runoff during summer Signup and view all the answers

Which factor has the least impact on stream erosion according to the content?

Soil fertility Signup and view all the answers

Moderate resistance to physical weathering is typically associated with which lithology?

Sedimentary rock Signup and view all the answers

Which geologic structure is characterized by a steeply dipping ridge formed from less erodible layers?

Hogback Signup and view all the answers

Which type of drainage network typically results from steep terrain areas?

Radial Signup and view all the answers

If two areas have the same drainage basin size, which factor would likely lead to higher drainage density?

Steeper slopes Signup and view all the answers

What is the primary influence of lithology on stream erosion rates?

Resilience to weathering Signup and view all the answers

Which geological feature is least likely to be affected by stream erosion?

Alluvium Signup and view all the answers

Which climatic factor would most likely lead to reduced streamflow over time?

Rising temperatures Signup and view all the answers

What leads to a higher rate of erosion in a drainage basin?

Higher drainage density Signup and view all the answers

Which drainage pattern is characterized by streams radiating outward from a mountain or volcanic peak?

Radial Signup and view all the answers

In which drainage pattern do streams follow right-angle bends and are often influenced by faults?

Rectangular Signup and view all the answers

What defines a superimposed stream?

A stream maintaining its course despite underlying geological structure Signup and view all the answers

What does the recurrence interval measure in terms of flooding?

The average time between floods of a given magnitude Signup and view all the answers

Which drainage pattern is most commonly found in landscapes with gently sloping and uniform bodies of rock?

Dendritic Signup and view all the answers

What type of stream predates the geological features it erodes, being influenced by tectonic uplift?

Antecedent stream Signup and view all the answers

Which statement about flood types correctly distinguishes bankfull from overbank floods?

Bankfull floods are frequent and cause less damage than overbank floods. Signup and view all the answers

What is the primary process by which rainwater contributes to soil erosion on slopes?

Rainsplash erosion Signup and view all the answers

How does vegetation influence the erosion process in river systems?

Stabilizes soil and reduces runoff Signup and view all the answers

What term refers to the total area from which a river system collects its water?

Drainage basin Signup and view all the answers

Which of the following is NOT a method of river erosion?

Suspension Signup and view all the answers

What is meant by the term 'stream power' in the context of river systems?

The river's potential to erode or transport sediments Signup and view all the answers

Which factor primarily determines a river's transport capacity?

Discharge rate Signup and view all the answers

Which form of erosion involves the mechanical abrasion of a riverbed by particles carried in the water?

Abrasion Signup and view all the answers

What describes sediment yield in the context of river systems?

The mass of sediment leaving a stream basin per year Signup and view all the answers

How does sediment load in a river affect its flow characteristics?

Alters the river's transport capacity and velocity Signup and view all the answers

What is the ultimate base level for rivers?

The lowest elevation a river can reach, typically sea level Signup and view all the answers

Which type of erosion refers to the breaking apart of rocks and sediments due to collisions with each other?

Attrition Signup and view all the answers

Which of the following factors could reduce sediment yield in a river system?

Increased vegetation cover Signup and view all the answers

What force primarily drives water to flow from high to low elevation in rivers?

Hydraulic gradient Signup and view all the answers

Study Notes

Increasing Temperatures and Ablation Zone

Increasing temperatures can expand the ablation zone.
This is the area of ice loss during warmer seasons.

Precipitation and Accumulation

Precipitation in colder seasons contributes to ice sheet accumulation.
Rainfall, however, runs off the ice sheet, failing to contribute to accumulation.

Continental Configuration and Ice Sheet Growth

Plate tectonics significantly influences ice sheet growth.
The presence of continental crust near the poles is crucial for forming large ice sheets.
This provides a stable platform for ice sheet development at the coldest regions, above sea level.

Last Interglacial – Eemian (130-115 ka)

CO2 levels were around 290 ppm during the Eemian period.
Current CO2 levels are approximately 420 ppm.

Last Glacial Maximum (LGM) - Laurentide Ice Sheet

The LGM occurred approximately 24-20 thousand years ago, marking the peak of the last glacial period.
The Laurentide Ice Sheet was extensive during this time.
Global temperatures were around 6 degrees Celsius lower than present.

End of the Last Glacial Maximum (LGM)

Ice sheet margins retreated following the LGM, signifying warming and deglaciation.

Paleoclimatology

The study of past climate change.
Offers insights into the Earth's climate history.

Greenhouse Gas Feedback: CO2 Solubility

Decreasing temperatures lead to colder water.
Colder water can absorb more CO2 from the atmosphere, creating a positive feedback loop.
This results in further cooling.

Greenhouse Gas Feedback: Permafrost

Permafrost thaw releases methane and carbon dioxide, leading to warming and further permafrost thaw.
This represents a positive feedback process.

Greenhouse Gas Feedback: Iron Fertilization

Cold, dry conditions lead to increased dust, which carries nutrients to the oceans.
This increased nutrient availability boosts phytoplankton growth, which absorbs carbon dioxide.
The process contributes to a positive feedback loop, further reducing temperatures.

Ice-Albedo Feedback

A positive feedback loop where changes in ice cover impact the amount of solar radiation reflected back into space.
Ice reflects more sunlight, causing a cooling effect.
As temperatures rise, ice melts, reducing reflectivity, leading to further warming.

Glacial-Interglacial Transitions

Milankovitch cycles, driven by changes in Earth's orbital configuration, affect incoming solar radiation.
These variations are amplified by greenhouse gas positive feedback loops and albedo changes.

Accumulation vs. Ablation

Accumulation refers to the gain of snow and ice on an ice sheet, while ablation is the loss of ice through melting or other processes.
The equilibrium line marks the balance point between accumulation and ablation.
The balance between the two determines the overall growth or retreat of ice sheets and glaciers.

Climate Factors for Ice Sheet Growth

Summer temperatures play a crucial role in ice sheet growth or retreat.
Lower summer temperatures facilitate ice preservation and growth, while higher temperatures accelerate ablation.
Precipitation in the form of snow during colder seasons contributes to accumulation.
Rain, however, runs off without adding to the ice sheet.

Periglacial Environments

Permafrost, which prevents drainage, contributes to saturated soils even in areas with low precipitation.

Continuous vs. Discontinuous Permafrost

Continuous permafrost exists when frozen ground is present throughout the area.
Discontinuous permafrost demonstrates patches of frozen ground interspersed with unfrozen areas.
Continuous permafrost typically occurs at higher latitudes or elevations due to colder conditions.

Pingo Formation

Pingos are mounds in periglacial landscapes.
These mounds form when water infiltrates the soil after thawing, subsequently freezing to form a lens of ice that pushes up the overlying soil.

Glacial-Interglacial Cycles: Milankovitch Cycles

Milankovitch cycles are primarily responsible for driving glacial-interglacial cycles.
These cycles involve changes in Earth's orbital parameters, including eccentricity, axial tilt, and precession, influencing solar radiation reaching Earth.

Ice Sheet Ablation:

Ablation, or the loss of ice from an ice sheet, is primarily driven by melting during warmer seasons.

Drainage Density

Drainage density: Total length of stream channels in a given part of a drainage basin.
Higher drainage density indicates a higher rate of erosion.

Drainage Patterns

Radial: Streams radiate outward from a central high point, like a mountain or volcano peak.
Annular: Streams flow around a high point, separated by ridges, forming a circle around the peak.
Trellis: Parallel streams form due to layers of sloped/folded sedimentary rocks and resistant ridges.
Rectangular: Streams create right angles, often associated with faults.
Dendritic: Streams resemble a tree's branching structure, forming on gently sloping, uniform rock. This is the most common drainage pattern.

Stream Types

Superimposed Stream: Maintains its course despite underlying structural changes. Forms on horizontal beds overlying folded/faulted rock, indicating structural changes predate the stream.
Antecedent Stream: Predates the ridge it erodes. The stream forms before the ridge is lifted by tectonic activity, implying the stream predates the structural change.

Stream Piracy

One stream captures a segment of another stream.
The captured stream's former channel becomes a "dashed blue line" on a diagram.

Floods

Bankfull: Stream fills its largest channel size, frequent, and less damaging.
Overbank: Stream overflows its channel, infrequent, and more damaging.

Recurrence Interval

The average time between floods of a given magnitude in a given location.

River Systems

Trunk: The main part of the river system (e.g., the Mississippi River).
Tributary: Smaller streams that feed into the trunk.
Drainage Basin or Watershed: The full network of trunk and tributaries, encompasses the area where water flows into the river system.

Fluvial Processes

Water flows from high elevation to low elevation.

Erosion

Rainsplash Erosion: Raindrops dislodge and scatter soils downslope.
Sheet Erosion: Runoff channels carve into surface soils/sediments when precipitation rate exceeds infiltration rate, resulting in water running across the surface.

River Sediment Transportation

Dissolved Load: Minerals dissolved in the water and transported.
Suspended Load: Fine particles carried by the river's flow.
Bed Load: Larger particles that roll or slide along the river bed.

River Sediment Characteristics

Transport Capacity: The maximum amount of sediment a stream can carry at a given discharge.
Competence: The largest particle size a stream can set in motion.

Sediment Yield

The mass of sediment leaving a stream basin per year.

Stream Power

The stream's ability to do work, such as moving sediment.
Increases with discharge and slope.

Base Level

The lowest elevation to which a river can erode.
Ultimate Base Level: Sea level.
Local Base Level: A temporary base level, such as a lake or a larger river.

Factors Influencing Stream Erosion

Climate Change: Affects minimum annual streamflow, impacting the water's erosive power.
Lithology: Rocks' resistance to weathering (physical and chemical) influences erosion rates. Different rocks erode at different rates, creating varying slopes.
Geologic Structure:
- Hogback: Steeply dipping ridge formed by less erodible layers.
- Cuesta: Shallow dipping, erosion-resistant layers forming an asymmetrical ridge.
- Ridges and Valleys: Formed by the differential erosion of resistant and less resistant rocks.
- Domes: Upwardly arched rock formations with dipping layers.
- Faults: Fractures in the Earth's crust that can influence erosion patterns.
- Plateaus, Mesas, Buttes: Flat-topped landforms formed by resistant igneous rocks.

Landscape Evolution Theories

An ongoing area of research in geomorphology.
Geomorphologists study how regional landscapes are shaped.

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Description

Explore how climate factors such as temperature, precipitation, and continental configurations influence the growth and loss of ice sheets. This quiz covers historical periods, including the Last Interglacial and Last Glacial Maximum, providing insights into ice dynamics and climate interactions.