Earth Science Note – Volcanism, Metamorphism, Deformation, Plate Tectonics, Relative and Absolute Dating, Geologic Time Scale

Summary:

This Earth Science note covers various geological concepts, including volcanism and metamorphism, faults, stress, strain, folding, and plate tectonics. It explains the different types of volcanic eruptions and materials produced, the process of metamorphism, and the various types of metamorphism. The article also discusses plate tectonics theory, the movement of plates, and plate boundaries and interactions. Additionally, the article covers methods for dating rocks and fossils, including relative dating and absolute dating using radioactive decay, and the Geologic Time Scale, which divides Earth’s history into eons, eras, periods, and epochs. The different periods within each era are described, along with major events and life forms that existed during those periods.

Excerpt:

Earth Science Note – Volcanism, Metamorphism, Deformation, Plate Tectonics, Relative and Absolute Dating, Geologic Time Scale

Volcanism
Earth’s internal heat
• Drives most geological processes including volcanism and plate tectonics
• Leftover heat from its formation 4.54 billion years ago
• Disintegration of natural radioactive elements inside the earth
• Earth’s core is about 5000-7000 degrees Celsius

Magma
• Molten rocks found beneath Earth’s surface
• Less dense than surrounding rock, therefore capable of rising to the surface
• Lava – when magma emerges at the surface
• Composed of elements such as silicon, aluminum, iron, calcium, magnesium, sodium, potassium,
hydrogen, and oxygen.
• Common component is silica (SiO2) at 45-75% by weight. Gases such as water vapor and carbon
the dioxide is present at 0.2-3% by weight.
• Has very high temperatures ranging from 800C to 1400C
• The degree of resistance to flow is called viscosity. The viscosity of magma depends on its silica
and gas content ad temperature.
• Magma with high silica – more viscous; Magma with higher gas content and temperature – less
viscous.

Formation of Magma
• Decompression Melting – temperature stays the same, but the pressure exerted decreases.
Occurs in rift valleys and mid-ocean ridges.
• Flux Melting – gaseous substances are added into the hot solid rocks where it react with rocks
and weakens them, causing them to change from a solid state to a liquid. Occurs in subduction
zones.
• Heat Transfer Melting – melting of surrounding rocks caused by hot magma bringing additional
heat. Occurs in hotspots.