Topic 5: Fossil Fuel Energy Flashcards
What is the most general path of the carbon cycle?
- CO2 in the atmosphere, taken into trees and plants via photosynthesis
- organisms in the ocean take in Co2
- carbon goes back into the atmosphere at night, via respiration
- soils give carbon back to the atmosphere via decay
oceans give some carbon back to the atmosphere - burning fossil fuels and cement production produces a ton of carbon to the atmosphere
What is the carbon cycle?
- how carbon is exchanged between reservoirs via interconnected pathways
- includes terrestrial biosphere, geosphere, hydrosphere, and atmosphere
Where is carbon stored/exchanged in the terrestrial biosphere and geosphere?
terrestrial: plants and animals, freshwater systems, and soil carbons
geosphere: fossil organic carbon in sedimentary sequences. Carbon in carbonate rocks and other igneous bodies
Where is carbon exchanged in the hydrosphere and atmosphere?
hydrosphere: marine biota, lots of dissolved carbon in the deep ocean, slowly is exchanged with the atmosphere. Ocean is the largest active carbon reservoir
atmosphere: atmospheric CO2, igneous outgassing, combustion, etc.
What is a carbon sink? carbon source?
Sink: takes in more carbon than it puts out. Oceans and forests are huge carbon sinks
Sources: puts out more carbon than it takes in. Weathering of rocks, melting permafrost, agriculture, and abuse of fossil fuels are all climate SOURCES
What are the three common formation processes for fossil fuels?
- Biogenesis
- Catagenesis
- Metagenesis
What is biogenesis?
- first stage in fossil fuel formation
- breakdown of complex organic materials by archaea, after burial under anoxic conditions
- archaea produce methane
- this occurs in shallow sedimentary settings
What is catagenesis?
- the second stage in fossil fuel formation
- “cracking” - chemical breakdown of organic kerogens to form hydrocarbons
- times, temperature and pressure dependent process
- produces bituminous coal, petroleum, methane. ect.
- occurs in medium to deep sedimentary settings
What are kerogens?
- mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks, halfway stage to full hydrocarbon
What is metagenesis?
- the third and final stage to fossil fuel formation
- low grade burial and regional metamorphism
- water is expelled from pore spaces in the rocks, liquid hydrocarbons expelled
- production of thermogenic methane (called dry gas - cause it has very little water in it
- everything that is NOT carbon gets driven off at methane, increase in carbon content
- occurs in deep sedimentary or orogenic settings
What is “jet”? the two kinds?
Jet is high pressure alteration of wood from trees of the family Araucariaseae
- soft jet is carbon compression in freshwater
- hard jet is carbon compression in salt water
there were no coals before the _______, because…..
there were no coals before the Devonian, because this is when evolution of terrestrial plants occurred.
pre- Mesozoic coals were denominated by _________, while mesozoic and paleogene coals were dominated by __________
pre- Mesozoic coals were denominated by ferns and scale-trees, while mesozoic and paleogene coals were dominated by _flowering plants and trees
What are the two coal types?
- Humic coals
- sapropelic coals
What are humic coals?
- coal made from fibrous plant debris
- contains Macerals, which is a lustrous black mineral-like material.
- formation is: Plants —> Peat —> lignite —> bituminous coal
What are sapropelic coals?
- formed from sapropels, fine-grained featureless algal debris
- forms in anoxic lakes, pools, ponds
- no oxygen, rich nutrients
How does coal formation occur in a swamp setting?
- organic debris accumulates in wet anoxic environment
- the low oxygen and acidity limit the decomposition of anything that sinks to the bottom
- typically has high peat accumulation in temperate regions.
How does coal formation occur in a transgression-regression setting?
- transgression: relative to sea level rise, covers land up
- regression: relative to sea level fall, exposes previously covered land
- interbedded coal and shallow marine clastic and carbonate sequences
- considerable lateral variation of coal deposits that reflects variations in swamp environments
what were some of the major coal-forming periods?
- carboniferous (max coal production, lots of vegetation)
- jurassic to paleogene (second major coal forming interval)
Where is modern coal accumulated?
- florida, virginia, coastal areas of canada, ireland, scandinavia
Why are there no long-term coal accumulation in temperate regions today?
- due to glacial activity
- glacial isostatic sea level change
what is the post-depositional modification part of coal formation?
- compaction and bacterial and fungal attack
- lots of compression
- production of methane, co2, ammonia (gases escape)