GLY 101: Earth Revealed Study Notes

GLY 101: Earth Revealed

Instructors and Logistics

• Course Title: GLY 101 Earth Revealed

• Semester: Fall 2025

• Instructor: Dr. Emma Morris

Geological Time

• Overview of Geological Time Scale, highlighting significant periods and epochs in Earth's history.

Major Extinction Events

• Cretaceous-Paleogene (K-Pg) Extinction: Gigantic extinction event approx. 66 million years ago.

• Big, Big Extinction: Refers to extensive extinctions over geological time periods.

Geological Timescale Overview

• Eons and Eras:

  • Cenozoic Era

    • Timeframe: 0 - present

    • Includes: Holocene (10,000 years ago), Pleistocene, Pliocene, Miocene, Oligocene, Eocene, Paleocene

  • Mesozoic Era

    • Timeframe: 252.2 - 66 million years ago

    • Includes: Cretaceous, Jurassic, Triassic

  • Paleozoic Era

    • Timeframe: 541 - 252.2 million years ago

    • Includes: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian

  • Proterozoic Eon

    • Timeframe: 2.5 billion - 541 million years ago

    • Evolution of early life forms and geological processes.

  • Archean Eon

    • Timeframe: 4.0 - 2.5 billion years ago

    • Formation of the first stable continental crusts.

  • Hadean Eon

    • Timeframe: 4.6 - 4.0 billion years ago

    • Earth’s formation.

Geological Time Scale Visuals

• Graphic Representations: Include graphs and diagrams to visualize the timing of eons and their subdivisions.

Hadean Eon (4.6 - 4.0 billion years ago)

• Characterized by:

  • Formation of Earth

  • Development of early atmosphere

  • Formation of oceans

Key Findings

• Zircon samples from Jack Hills, Australia, dating back to 4.4 billion years show evidence of liquid water, indicating a more temperate climate early in Earth's history.

Archean Eon (4.0 - 2.5 billion years ago)

Formation of Continental Crust

• Geological Features:

  • Formation of proto-continents and volcanic activity led to the production of specific rock types.

  • Four key rock types known as the 'four G's':

  • Gneiss: Indicates proto-continental crust formation.

  • Greenstone: Represents proto-oceanic crusts.

  • Graywackes: Sandstones from early oceans.

  • Granites: Later-stage intrusion rocks.

Life in the Archean

• Origin of Life: First chemical evidence dates to approximately 3.5 billion years.

• Fossils: Earliest bacterial fossils identified at around 3.2 billion years old, including ancient stromatolites.

• Modern Stromatolites: Found in Shark's Bay, Australia; evidence from Greenland and Australia dating back to approximately 3.5 billion years.

Proterozoic Eon (2.5 billion - 541 million years ago)

Continental Crust and Supercontinents

• Major supercontinents:

  • Nuna/Columbia Supercontinent: Existed between 1.8 - 1.3 billion years ago.

  • Rodinia Supercontinent: Existed between 1.1 - 0.7 billion years ago.

  • Pannotia Supercontinent: Existed between 0.6 - 0.5 billion years ago.

Oxygenation Events

• Significant increase in atmospheric oxygen between 2.4 to 2.2 billion years ago due to cyanobacteria.

Snowball Earth

• Events of global glaciation during the Proterozoic, leading to significant climatic changes and atmospheric composition shifts.

Ediacaran Fauna

• Ediacaran Period (635 - 538.8 million years ago):

  • Known for early multicellular life including soft-bodied organisms that resemble modern-day jellyfish, worms, and soft corals.

  • Fossils found worldwide including locations in Australia and China.

Phanerozoic Eon (541 million years ago - present)

Paleozoic Era (541 - 252 million years ago)

• Significance:

  • Marks significant diversification of life, particularly marine animals.

• Cambrian Explosion: Rapid development of hard-shelled animals and skeletal frameworks.

• Key paleogeography details:

  • Breakup of the supercontinent Pannotia into smaller continents.

Cambrian and Ordovician Life

• Emergence of significant marine life forms including trilobites, brachiopods, and coral species.

• Mass extinction events during the Ordovician affecting diverse marine families.

Silurian and Devonian Periods

• Known as the "Age of Fishes," transitioning to more complex animal life.

• Development of jawed fishes, and terrestrial plants began to emerge.

Late Paleozoic

• Carboniferous Period: Development of extensive swampy forests and rich coal deposits, development of amphibians.

• End-Permian Mass Extinction: "The Great Dying." This mass extinction event caused the extinction of approximately 80-90% of species, clearing ecosystems globally.

Causes of End-Permian Extinction

• Volcanic activity (Siberian Traps) emitting greenhouse gases leading to global warming and acid rain.

Mesozoic Era (252 - 66 million years ago)

• Triassic, Jurassic, and Cretaceous Periods: Known for the dominance of dinosaurs and the development of new plant life.

• Important paleogeographic changes characterized by tectonic shifts and continental moves.

Cenozoic Era (66 million years ago - present)

• Overview of evolutionary developments leading to modern mammals and the emergence of humans.

• Climate and geographic changes, including the formation of modern mountain ranges and the influence of glaciation on present-day landscapes.

Useful Web Resources

• Wikipedia: Evolutionary History of Life

• University of California Berkeley, Web Time Machine

• Dr. Ron Blakey, Northern Arizona University, Paleogeographic Maps

• PBS: Cracking the Ice Age

• NASA Science: The Great Dying

These notes provide a detailed overview of geological time, focusing on significant eons, eras, events, and fossil records as presented in the course materials. They include critical information on the formation of the Earth and the life forms that emerged over geological history, the mass extinctions that shaped the evolution of species, and the geological and paleontological importance of each period.