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LS2H03- Short Answer REVIEW pdf.pdf

11 Pages
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Department
Life Sciences
Course Code
LIFESCI 2H03
Professor
Luc Bernier

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Description
Sara  Malik                                                                                                                                                                                           LS2H03-­‐  2013  FINAL  EXAM  SHORT  ANSWER  REVIEW   Life Science 2H03- Short answer REVIEW 1. Milankovitch Theory (Lecture 9: Long term climate change) • Ice growth in the northern hemisphere occurs when: summer insolation is low • Isolation would need to persist over thousands of years to see an effect • Leads to less melting Aphelion= far from the sun Perihelion= Close to the sun · Ice sheets at the poles leads to cooling of the oceans, and the solubility of CO2 is affected. More CO2 and less in atmosphere, which increases photosynthesis Milankovitch's theory predicts that the gravitational influences of the Moon and the other planets, combined with Earth's slightly nonspherical shape, induce small but important variations in Earth's orbital parameters. These variations affect the amount of summertime insolation at high northern latitudes, triggering the onset and end of glacial intervals Orbital (Milankovitch) theory provides the answer to the question of causation of glacial–interglacial cycles. a. Small changes in the configuration of Earth's orbit around the Sun, varying in a predictable fashion, have provided the slight changes in seasonal insolation necessary to initiate these climate swings. These include changes in orbital eccentricity, obliquity, and the precession of the spin axis. b. The climate response matches the relative magnitude of the forcing at the frequencies of the precessional and obliquity changes. c. However, the dominant periodicity of glacial– interglacial fluctuation is 100,000 years. The forcings from eccentricity changes at this periodicity are too small. Sara  Malik                                                                                                                                                                                           LS2H03-­‐  2013  FINAL  EXAM  SHORT  ANSWER  REVIEW   2. Chemical Weathering and Climate Feedbacks (Lecture 9) Chemical Weathering - Plausible explanation for changes in CO2 levels (Early atmosphere rich in CO2) Intro to Chemical Weathering - Chemical weathering changes the composition of rocks, often transforming them when water interacts with minerals to create various chemical reactions. Chemical weathering is a gradual and ongoing process as the mineralogy of the rock adjusts to the near surface environment. New or secondary minerals develop from the original minerals of the rock. In this the processes of oxidation and hydrolysis are most important. - Chemical weathering takes place in almost all types of rocks. Smaller rocks are more susceptible because they have a greater amount of surface area - Chemical reactions break down the bonds holding the rocks together, causing them to fall apart, forming smaller and smaller pieces. - Chemical weathering is much more common in locations where there is a lot of water, because water is the most important feature to the chemical reactions - Warmer temperatures are more friendly to chemical weathering - The most common types of chemical weathering are: o Oxidation: takes place when oxygen combines with another element in rocks to form new type of rock, product is usually much softer, and easier for other forces to break apart) o Hydrolysis: when water combines with the substances in rocks to form new types of substances, which are softer than the original rock types, allows mechanical weathering to break them apart easier and carbonation o Carbonation: Takes place when carbon dioxide reacts with other types of rocks forming a solution that can easily be carried away by water Chemical weathering and Carbon dioxide* - The chemical weathering process of carbon dioxide in the atmosphere dissolving in rainwater to form carbonic acid, which dissolves rocks and then flows into the oceans, stores around 0.3 billion tons of atmospheric carbon in rivers and in the oceans every year - The carbon dioxide in the atmosphere dissolves in rainwater forming carbonic acid, which, once in contact with rocks, slowly dissolves them. This atmospheric carbon is then transported by rivers into the oceans, where it is trapped for several thousand years, before returning to the atmosphere or alternatively being stored in marine sediments or in corals. Sara  Malik                                                                                                                                                                                           LS2H03-­‐  2013  FINAL  EXAM  SHORT  ANSWER  REVIEW   Carbon Cycles Constantly Between Earth’s Interior and its Surface · In the ocean carbon dioxide will be released to the surface at the ridges · On land carbon dioxide will be released from volcanoes · The rate at which CO2 is released and the rate at which it’s deposited back to the ocean varies over time Hydrolysis & Removal of CO2 from the Atmosphere · e.g. Dissolution of CaSiO3 (Wollastonite) Biological Weathering of Silicate Rocks · Over time bacteria and fungi colonize and cause weathering of the rocks · Abiotic Exposed to the same conditions (no life, no bacteria) · Biotic Exposed to life, bacteria Sara  Malik                                                                                                                                                                                           LS2H03-­‐  2013  FINAL  EXAM  SHORT  ANSWER  REVIEW   The Inorganic Carbon Cycle · Ultimately: No net chemical change · Magma will be rich in silicate rocks Chemical weathering acts as a: Sara  Malik                                                        
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