Historical Geology - Chemical Cycles Flashcards
What is a (chemical) reservoir?
A body of chemical entities that occupy a particular space.
What is a feedback mechanism?
An influence that either accelerates or opposes the expansion of a reservoir
What is carbon?
Building block of life
How is carbon used (stored and released) in vegetation?
- plants store energy as sugar via photosynthesis
- plants release energy via respiration (metabolism)
creating a photosynthesis respiration cycle.
What results in carbon storage?
Tissue growth - more biomass means less carbon available for other reservoirs
What is decomposition?
Decomposers break down organic matter through respiration taking in O2 and respiring CO2.
How do animals fit into the carbon cycle?
Plants produce O2 in respiration, animals take in O2 and respire CO2 which the plant uses with water and sunlight in photosynthesis.
What alters atmospheric reservoirs of carbon and oxygen over geologic time?
If organic matter is buried it will not decompose and therefore emit CO2. This is balanced over long periods of time with erosion.
How is a reservoir depleted?
High rates of burial result inlower atmospheric carbon content In turn, this results in a higher atmospheric oxygen content
What is the green house effect?
Trapping of solar radiation by the earth’s atmosphere that warms the earth’s surface.
What are green house gasses?
(CO2, methane (CH4), water vapor)
warm atmosphere by absorbing infrared radiation (i.e., heat)
Explain Isotopic fractionation.
- transfer of isotopes from one mixture to another resulting in compositional changes to both mixtures
- measurements reported in δ notation (eg δ13C)
- calculated using the ratio of the heavy isotope divided by the lighter isotope
- δ18O = (Rsample – Rstandard / Rstandard) x 103
How do you measure isotope ratios?
use mass spectrometry
What else can affect atmospheric levels of CO2
Weathering (collectively, the chemical and physical processes that break down rocks) is the primary process that uses up CO2 from the atmosphere.
What geologic processes are involved in decreasing atmospheric CO2?
- Mountain building – does it accelerate or slow down weathering?
- Climate – High amounts of water and higher temperatures generally cause chemical reactions to run faster. Warm humid tropical climates generally have higher rates of weathering than in cold dry climates.
- Vegetation – Increased moisture results in more forest cover, and the roots of large plants accelerate chemical weathering (roots secrete acids that break down minerals).
- Animals – burrowers such as rodents, earthworms, and ants bring material to the surface were it can be exposed to the agents of weathering.
Is rock type important in weathering? Why?
Yes Rock type is important! Different rocks are composed of different minerals, and each mineral has a different susceptibility to weathering
What is the make of of Oxygen and its stable isotopes?
8 protons
Stable isotopes are 16O, 17O, and 18O
How do oxygen isotope ratios vary?
- position within the cycle (ocean, clouds, precipitation)
- salinity
- glacial ice
What can you use to interpret ocean temperatures through time?
benthic foraminiferan skeletons
Isotopic oxygen ratios incorporated into the skeleton
What happens in an icehouse climate?
- Glaciers advance
• Storing lots of light oxygen (16O)
• What will this do to our δ18O values? - Sea level drops
• By several hundred meters in some cases - Albedo effects increase
• Snow/ice reflect up to 90% of radiant energy from sun - Vegetation retreats towards the equator
What happens in a greenhouse climate?
- Albedo effect decreases
- Sea level rises
- Vegetation expands towards poles
- Increase in coral reefs and carbonate deposits
What do early eocene fossils indicate about climate?
example
Palm trees cannot withstand freezing temperatures but they were found as far north as Alaska in the Eocene era leading us to believe it was warmer at higher latitudes in the Eocene era.
