GEOL 362 Chapter 1 - A Changing Planet

Formation of Earth

• Gas and dust particles are attracted gravitationally and shrink, rotate, and flatten

• Temperature rises at center of disk, prompting chemical reaction where hydrogen nuclei fuse to form helium → large release of energy = sun

• In outer rings of disk, floating debris collides and grows until they form large gravitational force, called protoplanets

• Proto-Earth collides with Theia, creating current Earth and moon

Early life

First lifeforms were bacteria and algae, not much different from modern forms as ability to adapt and general survivability better than ecological niche adaptations that make it vulnerable to changes

Geochemical reason for decline in atmospheric CO2

CO2 dissolve in atmospheric water droplets fell as acid rain and reacted with rocks (weathering), storing CO2 in Earth’s crust

Biological reason for decline in atmospheric CO2

Early photosynthetic organisms used atmospheric CO2 for life processes, upon death trapped sequestered CO2 in sediment

Early oxygen

Photosynthetic organisms released this as a byproduct, but rate of increase in atmosphere initially low as it is a reactive gas with iron and other substances; after Great Oxygenation Event, major increase in concentration

Layers of atmosphere

Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

Troposphere

Layer of atmosphere 8-18km high, 80% of atmospheric mass is within this layer and is where weather phenomena occur; temp generally decreases with increase in height until tropopause

Tropopause

Upper limit of the troposphere, rate at which temp decreases compared to altitude declines

Stratosphere

Layer of atmosphere containing the ozone layer, its’ temperature increases with altitude due to absorption of UV rays

Evolution of aerobic life

Reactivity of oxygen = higher rate of energy release than non-oxygen counterpart, sexual reproduction also introduced more genetic diversity to accelerate evolutionary process until multicellular organisms formed

Carboniferous period

Era 360 to 300 million years ago with lots of plant/forest growth caused lots of carbon sequestration and coal formation

Climate

Average conditions in the Earth’s atmosphere, includes things like temperature, humidity, cloudiness, and how that affects Earth’s surface like desert and tropical environments (long term)

Weather

Immediate conditions of the local area, and changes in short timespans (eg. rainy, sunny, windy), short-term

Greenhouse effect

1. Radiation from sun passes through atmosphere and warms surface of the earth

2. Surface of Earth partially reflects radiation back into atmosphere and space, which is partially absorbed by greenhouse gases (water vapor, CO2) and redirected back to Earth, increasing its temperature

Negative feedback

When a stimulus causes a system to respond in a way that negates its initial effect (eg. increased temperatures cause greater evaporation of water → more precipitation → more weathering = more carbon sequestered and therefore decreases greenhouse gases in atmosphere and cools it)

Positive feedback

When a stimulus causes a system’s initial effect to be exacerbated (eg. white ice and snow have high albedos, which reflect more solar radiation into space → increases rate of energy absorption in atmosphere → heats atmosphere more, causing snow and ice to melt → melting reveals darker ground beneath which heats faster, causing increase in temperature)

Energy flows

An energy source that occurs at Earth’s surface at a steady rate regardless of whether it is being used (eg. sunlight, geothermal, tidal energy from earth and moon)

Fuels

Energy source that is stored in another form like in chemical bonds until it is deliberately converted (eg. coal, oil, natural gases, nuclear energy like uranium

Sunlight as an energy flow

30% rebounded back to space, 23% evaporates water and is stored in atmosphere until precipitation, only 1% is moving air and water, less than 0.1% is used in photosynthesis