Earth Science Introduction Notes

Introduction to Earth Science

What are Earth Sciences?

  • "Earth" is capitalized when referring to the planet.
  • "Moon" and "Sun" are also capitalized.
  • "Sciences" indicates that there are multiple Earth sciences.
  • The course provides a basic introduction to these sciences.

Geology

  • Considered the premier science among Earth sciences.
  • A pure STEM science (science, technology, engineering, and mathematics).
  • Incorporates physics, chemistry, and other sciences.
  • Geology is the study of Earth.
Divisions of Geology:
  • Physical Geology: Study of the materials that make up Earth (rocks, minerals).
  • Historical Geology: Study of Earth's origin and development, including fossils and concepts of time.

Oceanography

  • Study of oceans.
  • Oceans cover 71% of Earth's surface.
  • Oceans are the source of storms and waves.
  • The course will discuss the future of oceans.

Meteorology

  • Study of climate and weather.
  • Examines how climate and weather affect and are controlled by the Earth.

Astronomy

  • Study of the origin of the universe and the solar system.
  • The course will focus on the details of our solar system.

Scientific Method

  • The scientific method is how science works, progresses, and evolves. It has both strengths and vulnerabilities.
  • Assumptions: The universe is governed by understandable laws (e.g., gravity).
  • Data Collection: Gathering observations and data.
  • Hypothesis Formulation: Creating a testable question that explains the collected data.
  • Hypothesis Testing: Collecting more data to test the hypothesis.
  • Falsifiability:
    • If testing disproves the hypothesis, it is either modified or discarded.
    • A hypothesis is either true (answers the data) or false (does not answer the data).
  • Theory Development:
    • If test results align with predictions, the hypothesis may become a theory.
    • If a theory remains predictive over time, it may eventually become a law.
  • Laws are difficult to establish due to Earth's constant changes.
  • Example: Plate tectonic theory, while long-standing (since the 1960s), remains a theory due to the complexity of Earth systems and limited data, particularly from ocean basins.
  • Publication and Peer Review:
    • Proven hypotheses are published in scientific journals after peer review.
    • Editors send the work to multiple peers for evaluation and feedback.
  • Community Confirmation:
    • The scientific community reviews the data and confirms results and conclusions.
    • Researchers may use the same approach to solve other problems, validating the original findings.

Earth Time

  • Geology requires a time scale to explain Earth's history.
  • Rock layers are used like pages in a book to read Earth's history.
  • Stratigraphers, biographers, or historical geologists study rock layers.
  • They assemble Earth's history by studying different areas and combining the information.
  • This process started in the 1600s and is still ongoing.
  • Events must be placed in the correct order using the geologic time scale.

Catastrophic View of Earth History

  • An early perspective that Earth's features were formed by catastrophic events (e.g., floods, volcanic eruptions, storms).
  • Prevalent in the 14th-18th centuries due to a lack of understanding of Earth processes.
  • Volcanism influenced early thought, particularly after the eruption of Mount Vesuvius in AD 79.

Early Attempts to Date the Earth

  • Bishop James Usher (mid-1600s) estimated Earth's age to be approximately 6,000 years old.
  • Usher's Calculation: October 23, 4004 BC.
  • Based on biblical accounts and numerology, adding up genealogies and assigning ages.
  • His views were influential through the 1800s.

James Hutton and Uniformitarianism:

  • James Hutton (1700s) proposed that the same forces shaping Earth today shaped it in the past.
  • Observed slow changes over time (e.g., river flow, sandbar formation).
  • Included biological, chemical, and physical forces in his investigations.
  • Correctly noted that slow processes can cause huge changes over time.
  • Developed the concept of uniformitarianism: "The present is the key to the past."
  • This concept has been tested and is now a theory, potentially a law.

Environment and Resources

  • Environment: Anything that surrounds and influences an organism, including Earth's inorganic components.
  • Physical Environment: Non-living (inorganic) components.
  • Context: In Earth sciences, "environmental" usually refers to the relationship between humans and the physical environment.

Human Influence

  • Humans often believe they have a significant influence on Earth's physical environment due to activities like road construction and air travel.
  • This perception exists because Earth's system has stabilized.

Resources

  • Materials needed to maintain society.
  • Resource importance has changed over time (e.g., wood and wheat in the 14th-16th centuries, now different resources).

Environmental Problems

  • Humans interpret certain Earth events as problems, but Earth views them differently.
  • Earth is a vast system beyond human control.
  • Environmental problems are often cyclical, influenced by the sun, moon, Earth's orbit, and axis.

Why Study Rocks?

  • Rocks are made of minerals.
  • Minerals differ based on their formation environments.
  • Understanding these environments helps understand past Earth conditions (the physical environment).
  • Each mineral provides part of the story, and the group of minerals in a rock completes the story.

The Rock Cycle

  • Rocks undergo a cycle of transformation.
  • The Earth's early rocks were primarily igneous, often volcanic.
  • Weathering (chemical and mechanical) produces sediments, which can form new rocks.
  • Conditions within the Earth can create different rocks from the original ones.
Magma
  • Molten material within the Earth.
  • Can reach the surface through volcanic activity or by splitting Earth's crust (e.g., Rio Grande Rift, East African Rift).
Igneous Rock Formation
  • Magma cools and solidifies (crystallization) at or near the surface.
  • Example: Granite.
  • Weathering (mechanical and chemical) breaks down igneous rock into sediment.
  • Quartz remains as sand, while other minerals break down into clay and silt.
    • SiO_2 (Quartz)
Sediment Transport and Deposition
  • Sediments are transported by rivers, wind, and glaciers.
  • Deposited as sandbars, mud bars, or dust.
  • Lithification: Sediment is buried, cemented together, or compacted into sedimentary rock.
Sedimentary Rock Formation
  • Chemicals from weathered igneous rocks are transported and deposited.
  • Layers form over time (older layers at the bottom, younger at the top).
  • Geologists study rock outcrops from bottom to top to understand the history.
Metamorphic Rock Formation
  • Sedimentary rocks can be buried and subjected to high heat and pressure.
  • Metamorphism: A change in form of a rock due to increased heat and pressure.
  • Example: Limestone transforms into marble.
  • Marble Falls, Texas, is a source of marble, and Granite Shoals is a source of granite.
  • Metamorphic rocks show bending due to high heat and temperature, behaving like plastic or taffy.
Rock Classification
  • Igneous Rocks
  • Sedimentary Rocks
  • Metamorphic Rocks
The Complete Rock Cycle
  • With enough temperature and pressure, rocks melt and become magma again, restarting the cycle.
  • Igneous rocks can transform directly into metamorphic rocks.
  • Metamorphic rocks can be exposed, weathered, and transformed back into sedimentary rocks.
  • Sedimentary rocks can be eroded and reworked, eventually deposited in the ocean.

Earth's Internal Layers

  • Earth is differentiated by composition, chemical properties, and mechanical/physical properties.

Compositional Layers

  • Crust: Material comes from the mantle, but its chemical properties change at the surface.
  • Mantle: Layer underneath the crust. Chemically similar to crust.
  • Core: The heat engine of Earth, responsible for the magnetic field and heat production.

Mechanical Layers

  • Lithosphere: The outer, rigid layer, including the crust and outer part of the mantle (sphere of rocks).
  • Asthenosphere: A weak, plastic layer beneath the lithosphere (astheno means weak in Greek).
    • Lies between the core and the lithosphere, trapping heat.
  • Mesosphere: Transports heat from the Earth's interior toward the lithosphere.
  • Outer Core: Liquid iron and nickel.
  • Inner Core: Solid iron and nickel due to immense pressure.

The Geologic Column

  • Represents Earth's history over 4.5 billion years.
  • Shows the timeline of life: no life, single-cell life, multicellular life, plants, reptiles, dinosaurs, birds, and mammals.
  • Mass Extinctions: Five major mass extinctions are marked with skull and crossbones.

Plate Tectonics

  • The next topic to be covered.