Earth Science #1

Earth's Interior and Heat Sources

  • Layers of the Earth:

    • Crust

    • Upper Mantle

    • Outer Core (liquid)

    • Inner Core (solid)

  • Internal Heat Sources:

    • Primordial Heat:

      • Originates from Earth's formation; heat from accretion and impacts of planetesimals.

    • Radioactive Heat:

      • Produced by decay of radioactive isotopes; generates heat and geoneutrinos.

Temperature Inside the Earth

  • Temperature Gradient:

    • 15° to 30°C/km in upper 100 km; varies dramatically in deeper layers.

    • Approximate temperatures:

      • 1000°C (base of crust)

      • 3500°C (base of mantle)

      • 5000°C (Earth's center)

Heat Transfer Mechanisms

  • Conduction: Transfer of heat through materials.

  • Convection: Movement of heat via fluid motion, particularly in the mantle.

  • Radiation: Heat transfer through electromagnetic waves.

Magmatic Activity

  • Magmatism: Movement of magma stemming from molten rock due to temperature and pressure.

  • Plutonism: Formation of intrusive igneous rocks via solidification of magma beneath the surface.

  • Volcanism: Process of magma being released through volcanic openings.

Mechanisms of Magma Rise

  1. Density Contrast:

    • Magma is less dense than surrounding rock; rises faster with greater density contrast.

  2. Viscosity: Influences magma flow:

    • High temperature = low viscosity

    • High silica content = high viscosity.

  3. Magmatic Differentiation Processes:

    • Crystal Fractionation: Denser minerals crystallize first.

    • Partial Melting: Melting of specific minerals at high temperature/pressure.

    • Magma Mixing: Interaction of two different magmas results in intermediate magma.

Geological Processes - Impacts

  • Mantle Convection: Drives continental drift and seafloor spreading.

  • Magmatism: New crust formed as magma reaches the surface.

  • Volcanism: Generates geothermal energy, a valuable resource (e.g., in the Philippines).

Weathering Process

  • Weathering: Alteration and breakdown of rocks.

    • Physical Weathering: No chemical change (e.g., frost wedging, salt crystal growth).

    • Chemical Weathering: Alters chemical structure (e.g., hydrolysis, oxidation).

Types of Rock Deformation

  • Stress Types:

    • Tension: Plates move away; creates continental rifts.

    • Compression: Plates collide; forms mountains.

    • Shearing: Plates slide past; forms faults.

  • Factors:

    • Temperature: High temps lead to ductile behavior; low temps lead to brittleness.

    • Pressure: Alters likelihood of fracturing.

    • Strain Rate: Sudden changes cause brittle deformation; gradual changes lead to ductile deformation.

Metamorphism Types

  • Contact Metamorphism: Heat from igneous intrusions alters surrounding rocks.

  • Dynamic Metamorphism: High pressure along fault zones alters rock structure.

  • Regional Metamorphism: Occurs over broad areas due to tectonic forces, producing foliated rocks like schist and gneiss.

Plate Tectonics Overview

  • Plate Tectonics: Describes movement of Earth's lithosphere.

  • Boundaries:

    • Convergent: Plates collide, leading to subduction and mountain building.

    • Divergent: Plates move apart, forming rifts and new crust.

    • Transform: Plates slide past, often causing earthquakes.

Stratification of Rocks

  • Stratification: Layering within sedimentary rocks caused by sediment deposition.

  • Principles of Relative Dating:

    • Law of Superposition: Older layers below younger.

    • Principle of Original Horizontality: Layers originally deposited horizontally.

Dating Methods

  • Relative Dating: Arranging geological events by rock sequences.

  • Absolute Dating: Determining rock age via radioactive isotopes.

  • Index Fossils: Fossils used to estimate the age of rock layers; must be widespread and short-lived.