The Mesozoic Earth Flashcards
What is weathering? What is the difference between chemical and mechanical weathering?
The process that breaks down rocks and minerals due to environmental factors. Chemical weathering involves chemical reactions that alter the mineral composition, such as oxidation or dissolution. Mechanical weathering breaks rocks into smaller pieces without changing their composition, typically through physical forces like temperature changes, freezing and thawing, or abrasion.
What are three major chemical weathering processes? How do simple solution and hydrolysis differ?
Three major chemical weathering processes are oxidation, carbonation, and hydrolysis.
Simple solution refers to minerals dissolving directly in water, while hydrolysis involves a chemical reaction with water that alters the mineral structure.
What is the relationship between a mineral’s stability to chemical weathering and the order in which it
crystallises? Which minerals are most and least stable?
A mineral’s stability to chemical weathering is linked to its position in the Bowen’s Reaction Series, which shows the order in which minerals crystallize. Minerals that crystallize at higher temperatures are less stable and weather more easily. Minerals that crystallize at lower temperatures are more stable and weather more slowly.
Most stable: Quartz, feldspar, clay minerals.
Least stable: Olivine, pyroxene, amphibole.
What is the relationship between climate and weathering rates? How do rates of erosion vary with latitude?
Wet climates accelerate chemical weathering due to increased chemical reactions and moisture, while cold, dry climates slow down weathering processes.
At the equator, where it is warm and wet, erosion is faster due to higher rainfall and vegetation. At higher latitudes, erosion is slower because of cooler, drier conditions and less vegetation. In polar regions, erosion rates are low due to minimal moisture and freezing conditions.
Where do the residual products of weathering end up?
Clay, quartz, and other weathered minerals, typically end up in soils, sediments, or are transported by water to bodies like rivers, lakes, and oceans, over time they may compact to form sedimentary rocks.
What are the general trends in the climate and sea level through the Mesozoic? What are the names of the major Mesozoic continental masses and oceans and the approximate ages of their formation and break up?
The climate was generally warm, with higher global temperatures and no polar ice caps. This warmth contributed to high sea levels due to reduced ice volume and thermal expansion of ocean water
Pangaea (formed 335Ma) began breaking apart during Triassic, leading to the formation of smaller continents.
Laurasia and Gondwana: By the Jurassic (200Ma), Pangaea had split into these two major landmasses. Laurasia (North America, Europe, Asia) and Gondwana (South America, Africa, Antarctica, Australia, India).
Tethys Ocean: The Tethys Ocean began to close as Pangaea split and was located between Laurasia and Gondwana, eventually shrinking as the continents drifted apart.
Atlantic Ocean: The opening of the Atlantic Ocean began during the Jurassic, 180Ma, as the Americas rifted away from Europe and Africa.
Have all Large Igneous Province (LIP) eruptions resulted in mass extinctions? What controls their impact/severity on biota?
Not all LIP eruptions resulted in mass extinction.The impact of LIPs on biota depends on the volume of magma erupted, the rate of volcanic gas release, and the timing relative to other environmental stresses. Smaller or less intense eruptions may have more localized or less severe effects.
How do LIPs cause mass extinctions? How does increased levels of CO2 affect environmental feedback
relationships?
Rapid climate shifts, habitat disruption, and altered atmospheric conditions can severely affect ecosystems, leading to mass extinctions. Causes positive feedback loops leading to forest fires, melting of permafrost and melting of polar regions.
What is the name of the volcanic units that were erupted at the time of the Permo/Triassic mass extinction event?
Siberian Traps
What were the climatic conditions at the start of the Triassic? What is the evidence in the rock record of the
severity of the climatic conditions?
Hot and dry, with a greenhouse effect exacerbated by high levels of carbon dioxide and other gases from volcanic activity, particularly from the Siberian Traps.
Arid conditions: sedimentary rocks, like red beds and evaporites, suggest widespread aridity and the presence of dry, desert-like environments in many regions.
Oceanic anoxia: indicated by black shale deposits, points to disrupted ocean circulation and widespread marine die-offs due to changes in temperature and ocean chemistry.
Fossil records: reduction in biodiversity, especially marine life, is seen in the fossil record, with a significant loss of species at the end of the Permian.
Carbon isotope excursions: isotopic data from carbon in rocks shows a massive increase in atmospheric CO₂, supporting the idea of a greenhouse climate.
What is the name of the intensely humid interval within the Triassic (Carnian)? What was its cause?
How long did Pangaea last?
Carnian Pluvial Event. Likely caused by increased volcanic activity with the rifting of Pangaea, which released large amounts of carbon dioxide and other gases, leading to warming and changes in atmospheric circulation. This resulted in a wetter climate, particularly in the Carnian (230Ma).
Pangaea lasted until the late Triassic, 200Ma
When and in what order did Pangaea breakup? When did ocean floor spreading begin in the Central Atlantic? What land masses were created?
Pangaea began breaking up 200Ma, during the late Triassic to early Jurassic. It split into Laurasia (North America, Europe, Asia) and Gondwana (South America, Africa, Antarctica, Australia, India). Ocean floor spreading in the Central Atlantic started around this time. Over the Jurassic and Cretaceous periods, Gondwana further fragmented into smaller landmasses, creating the modern continents. The opening of the Atlantic Ocean and the rifting of Gondwana led to the formation of the continents we recognize today.
What was the name of the ocean between the two halves of Pangaea that existed during the Jurassic and
Cretaceous? What was the Tethyan trench and where was it located?
Tethys Ocean. The Tethyan Trench was a subduction zone. It marked the boundary where oceanic crust from the Tethys Ocean was subducted beneath the continental crust of Gondwana.
What was the cause of the end-Triassic mass extinction event?
201Ma, caused by a combination of volcanic activity, climate change, and possibly oceanic changes. Massive volcanic eruptions released carbon dioxide and sulfur dioxide, leading to global warming, acid rain, and ocean acidification, which caused severe disruptions in ecosystems.
The warming likely resulted in oceanic anoxia (lack of oxygen), which further stressed marine life. The disruption of ecosystems on land, including the loss of plant life, would have contributed to the extinction of many species.
What does OAE refer to, and what deposits are characteristic of these times? What is the relationship between OAE and LIPs?
Oceanic Anoxic Event, the deposits are black shales, which form when organic material is preserved due to the lack of oxygen, preventing decay.
LIPs release large amounts of greenhouse gases and sulfur compounds, causing global warming and altering ocean circulation. These changes can lead to ocean stratification, where the deep ocean becomes anoxic.
