ENV 100 - Modules 1-3

Earth Cycles, Cataclysmic Beginnings, Tectonics, Oceans. Lectures 1-6

Atmosphere

Layer of gases around the Earth.

Hydrosphere

All water on Earth.

Cryosphere

All water on Earth stored in ice. Subset of the hydrosphere.

Biosphere

Earth’s ecosystems. Also called the ecosphere.

Geosphere

The solid Earth.

Cycles

A series of events that are repeated regularly in the same order.

Temporal cycle

A cycle where events occur according to a timetable.

What is an example of a temporal cycle?

Seasonal cycle

Mass-transfer cycle

A cycle where objects physically move.

Geochemical cycle

A mass-transfer cycle involving physical components only.

Biogeochemical cycle

A mass-transfer cycle involving physical and living components.

Why are cycles crucial to Earth?

They regulate the climate, continuously recycle elements, maintain balanced ecosystems, and distribute nutrients.

Hydrological cycle

A series of processes and smaller cycles that move water through various states and stores.

Deep water cycle

Portion of the water cycle where water transports minerals to the Earth’s interior at subducting plate margins.

Small water cycle

Portion of the water cycle involving plants. The plant life cycle.

What are the key processes in the hydrological cycle?

Evaporation

Transpiration

Condensation

Precipitation

Interception

Infiltration

Percolation

Runoff

Storage

How have humans impacted the hydrological cycle?

Increased evaporation due to climate change and use of irrigation, decrease in infiltration/percolation dur to impervious surfaces, slowing downhill movement of water due to dams, increased runoff due to deforestation, decreased groundwater levels.

What are the two components of sea level rise?

Ocean water storage and thermal expansion.

Besides the deep water cycle, how does tectonics affect the hydrological cycle?

Landforms impact precipitation patterns (e.g. orographic rainfall).

Ocean water storage

Refers to changes in ocean water volume

What two factors cause changes in ocean water volume?

Movement of land (plate tectonics) and climate change (melting of ice/glaciers).

Thermal expansion

As water increases in temperature, it also increases in volume

Where does sea level tend to be higher?

At the equator

Where does sea level tend to be lower?

At the poles

Why does sea level tend to be higher at the equator than the poles?

Air pressure, variations, thermal expansion, and variations in the strength of gravity.

Milankovitch cycles

Three cycles that cause variations in Earth’s orbital movements.

What proportion of sea level rise is made up of ice melt?

60%

What proportion of sea level rise is a result of thermal expansion?

40%

How much of the Earth’s water is stored in the ocean?

96.5%

What are the three Milankovitch cycles?

Eccentricity, obliquity, precession.

Eccentricity

The shape of the Earth’s orbit - more circular vs. more elliptical.

Perfectly circular orbit

Eccentricity = 0

How does Earth’s eccentricity vary?

Between 0.0034 and 0.058.

How long is an eccentricity cycle?

100,000 years

Obliquity

The angle Earth’s axis is tilted with respect to its orbital plane.

How does Earth’s obliquity vary?

Between 22.1 and 24.5 degrees.

How long is an obliquity cycle?

41,000 years

Ice Ages tend to occur at ____ angles.

lower

Climates tend to be more extreme at ____ angles.

higher

Climates tend to be milder at ____ angles.

lower

Why do Ice Ages occur at lower angles?

Because the northern hemisphere summer is milder, so ice forms in the winter and does not melt.

Precession

The direction Earth’s axis of rotation is pointed.

How long is a precession cycle?

26,000 years

Solar forcing

The result of the interacting Milankovitch cycles.

How do Milankovitch cycles influence sea levels?

During colder periods, ice forms and sea level decreases. During warmer periods, ice melts and sea level increases.

Why does the climate in the northern hemisphere contribute more to global climate?

There is more land in the northern hemisphere, meaning that more ice and glaciers can form here than in the southern hemisphere.

El Nino Southern Oscillation (ENSO)

A climate cycle that occurs in the Pacific Ocean with relatively high frequency and alters global and regional climates.

What are the impacts of ENSO?

Flooding, drought, famine, mass marine dieoff.

How long is ENSO?

Generally around 5 years, but between 2-7 years.

Which direction do winds blow across the equator?

East-to-west

Which way do winds deflect in the 30 degrees north/south of the equator?

Winds from the north deflect southwest and winds from the south deflect northwest.

Upwelling

As warm surface water is removed, colder, nutrient-rich water rises to the ocean surface.

Upwelling ____ phytoplankton populations.

increases

Normal/neutral state

Trades winds drag warm water from the eastern Pacific to the western Pacific.

El Nino

Trade winds weaken or reverse, meaning that warm water stays in the eastern Pacific.

There is ____ upwelling in the eastern Pacific during El Nino.

less

Fish stocks in the eastern Pacific ____ during El Nino.

decrease

The Pacific Jet Stream moves further ____ during El Nino.

south

The climate in the eastern Pacific tends to be ____ during El Nino.

wetter

The climate in the western Pacific tends to be ____ during El Nino.

drier

Globally, surface temperatures ____ during El Nino.

increase

How much do surface temperatures increase during El Nino?

Around 0.1 degree

How long do El Nino events last?

Around 9-12 months

La Nina

Trade winds strengthen, so more warm water is dragged to the western Pacific.

There is ____ upwelling in the eastern Pacific during La Nina.

more

The Pacific Jet Stream moves further ____ during La Nina.

north

Fish stocks in the eastern Pacific ____ during La Nina.

increase

How does ENSO affect sea levels?

Thermal expansion causes sea levels to increase in the western Pacific during La Nina and increase in the eastern Pacific during El Nino.

Carbon cycle

How carbon dioxide is moved through different forms in the ocean, land, atmosphere, and Earth.

What are the key processes in the carbon cycle?

Photosynthesis

Respiration

Combbustion

Decomposition

Carbon sink

Storage

Which processes remove carbon dioxide from the atmosphere?

Photosynthesis, carbon sink, storage.

Which processes add carbon dioxide to the atmosphere?

Respiration, combustion, decomposition.

Where is the most carbon dioxide stored?

In sedimentary rocks

Where is carbon dioxide stored?

Sedimentary rocks, oceans, soil, atmosphere.

Photosynthesis

A part of the plant life cycle where carbon dioxide and water are taken in to make energy (glucose) for the plant and oxygen and a byproduct.

Respiration

Occurs when organisms use energy and output carbon dioxide.

Combustion

Burning

Decomposition

When dead organisms break down, releasing carbon dioxide into the atmosphere.

Carbon sink

The ability of a natural environment to absorb carbon dioxide form the atmosphere.

What are the two main carbon sinks?

Oceans and forests.

Storage

Carbon dioxide kept in reservoirs, often for a long time.

How much carbon dioxide do human emit each year?

9GT

Fast carbon cycle

The carbon dioxide recycled by living organisms, mostly through photosynthesis, respiration, and decomposition.

How does the fast carbon cycle vary over time?

It varies seasonally, due to different levels of vegetation cover throughout the year.

What timeframe does the fast carbon cycle act over?

Years/decades

Slow carbon cycle

The carbon dioxide recycled by slower processes, such as ocean absorption, tectonics, weathering, and glaciation.

What timeframe does the slow carbon cycle act over?

Tens/hundreds of millions of years

The slow carbon cycle is ____ affected by human activities than the fast carbon cycle.

less

How does the slow carbon cycle regulate Earth’s climate?

During periods of higher carbon dioxide levels, the climate is warmer and wetter, meaning that the rate of weathering is higher and more carbon dioxide can be absorbed by the ocean and turned into sedimentary rock. This cools the climate, which slows the rate of weathering.

What affects the slow carbon cycle most?

Volcanic activity

How do Milankovitch cycles affect the slow carbon cycle?

They cause changes in climate, which then affect the rates of weathering and ocean absorption of carbon dioxide.

Carbon capture and storage (CCS)

Methods created by humans to remove atmospheric carbon dioxide and move it into long-term storage.

What are the four steps in CCS?

Capture, transport, storage, monitoring.

Geosequestration

Storing of captured carbon underground in geological formations.

What kind of rocks are most suitable for carbon dioxide storage?

Porous rocks with high permeability and the right minerals to solidify carbon dioxide.

How deep should carbon dioxide be stored?

At least 800m below ground.

How does geosequestration work?

Liquified carbon dioxide is injected into porous rocks below the surface, under enough pressure for it to remain there.

How does geosequestration alter the carbon cycle?

It moves carbon dioxide from the fast carbon cycle to the slow carbon cycle.

Sedimentary rocks

Rocks formed by pieces of other rock and minerals/fossils of living organisms.

Metamorphic rocks

Rocks formed when heat and/or pressure is applied to other rocks, without melting taking place.