Deep Time

Overview of Dinosaurs and Geological Time

  • Discussion of dinosaurs' existence and extinction timelines

  • Transition into understanding geological time scale (deep time)

  • Use of an interactive module to explore geological time scale

Geological Time Scale

  • Definition: A method that breaks down the history of Earth into discrete time segments usually defined by significant geological or biological events.

  • The interactive geologic time scale allows exploration of:

    • Eons

    • Eras

    • Periods

Radiometric Dating

  • Importance: Determines the age of rocks using isotopic analysis.

  • Mechanism:

    • Natural breakdown of radioactive isotopes occurs over time.

    • Igneous rocks solidify from molten form with isotopic ratios equal to the environment.

    • Measure radioactive isotopes' ratio using mass spectrometers to estimate rock ages.

  • Limitations: Sedimentary rocks cannot often be used for radiometric dating because they are formed from eroded pieces of pre-existing rocks.

  • Application: Volcanic ash layers within sedimentary rocks can be dated to provide approximate ages for surrounding fossils.

  • Estimates of Earth's Age:

    • Oldest rock on Earth: approx. 4,400,000,0004,400,000,000 years old

    • Oldest rocks on the moon: at least 4,500,000,0004,500,000,000 years old

    • Formation of Earth: about 4,600,000,0004,600,000,000 years ago

Understanding Geological Time

  • Concept of geological time:

    • Difficult to visualize long timescales (e.g., 4,600,000,0004,600,000,000 years).

Eons of Earth's History

  • Hadean Eon (4,600 million years ago):

    • Formation of Earth and the Moon.

    • Environment: constant meteorite bombardment, partially molten surface, active volcanism, formation of oceans.

  • Archean Eon (4,000 million years ago):

    • Development of the first self-replicating RNA molecules in oceans.

    • Presence of single-celled organisms, dominated by bacteria and archaea.

    • Significant Event: Evolution of photosynthesis by cyanobacteria (~3.5 billion years ago).

  • Proterozoic Eon:

    • Dominated by single-celled organisms for extensive time.

    • Atmosphere becomes increasingly oxygenated.

    • First multicellular organisms originate around 1.7 billion years ago (fossils are rare due to size and soft bodies).

    • End of Proterozoic: Ediacaran period (~630 million years ago)

    • Fossils from this era are unique and do not closely resemble modern animals.

  • Phanerozoic Eon:

    • Characterized by significant development of multicellular life.

    • Divided into three eras: Paleozoic, Mesozoic, and Cenozoic.

Paleozoic Era

  • Cambrian Period: (540 million years ago)

    • Cambrian explosion: a rapid increase in diversity of multicellular organisms (not a literal explosion).

    • Notable life forms: sponges, mollusks, worms, trilobites, early vertebrates like Pikaea.

    • Significant Fossil Site: Burgess Shale (Canada).

  • Ordovician Period: (about 460 million years ago)

    • First fish (Estracoderms) evolved.

  • Silurian Period: (about 450 million years ago)

    • First organisms ventured onto land; terrestrial plants diversified.

  • Devonian Period: (about 370 million years ago)

    • Emergence of the first amphibians and lobe-finned fish.

  • Carboniferous Period:

    • Development of vast swampy forests contributing to today's coal deposits.

    • First reptiles appeared (~310 million years ago).

  • Permian Period:

    • Formation of Pangaea through continental collision.

    • Evolution of reptiles into three lineages: synapsids (mammal ancestors), diapsids (include modern reptiles), and anapsids (turtles).

    • Mass extinction event marking end of Paleozoic Era.

Mesozoic Era

  • Focus of the Course: Known as the age of dinosaurs.

  • Dinosaurs were the dominant vertebrates during this era.

  • First mammals appeared about 225 million years ago.

  • First birds evolved during the Mesozoic.

  • Closure: Another mass extinction at the end of the Cretaceous period marking the transition to the Cenozoic Era.

Cenozoic Era

  • Commonly referred to as the age of mammals as they became the dominant terrestrial vertebrates.

  • Development timeline:

    • Earliest primates evolved post-dinosaurs.

    • Apes evolved approximately 12 million years ago.

    • Emergence of modern humans (Homo sapiens) around 200,000 years ago.

    • All recorded human history has occurred within the last 10,000 years.

  • Visualization of Earth's History:

    • If the history of Earth (4.6 billion years) were condensed into 24 hours, humans would have existed for the last second of that time.

Conclusion

  • Current Era: Cenozoic Era.

  • Dinosaurs studied in this course lived during the Mesozoic Era.

  • Introduction to upcoming discussion on Mesozoic rocks, specifically from the Cretaceous Period, with Dr. Phil Curry.