โณ Deep Time: Geochronology & Mass Extinctions
Earth's crust is an immense stone archive spanning 4.54 billion years. Can you decipher the stratigraphic layers, calculate radioactive half-lives, and navigate the Big 5 mass extinctions?
How to play
- Explore 8 chronological horizons from the Hadean magma oceans and the Great Oxidation Event to the End-Permian "Great Dying" and Chicxulub asteroid impact.
- Click or tap any stratum in the interactive rock column to excavate index fossils, geochemical anomalies, and boundary dates!
- Use the Interactive Radiometric Decay Lab slider (0โ4 half-lives) to calculate parent-to-daughter isotope ratios and absolute crystal ages (t = n × t1/2).
- Apply Steno's Principles of Stratigraphy (Superposition, Original Horizontality, Cross-Cutting Relationships).
- Tap your answer or press 1โ4. Right answers build a ๐ฅ streak bonus!
โ๏ธ Interactive Stratigraphic Column (Click Any Layer to Excavate)
Superposition: Youngest Top → Oldest BottomAbout Deep Time, Mass Extinctions & Geochronology
The concept of Deep Time was first articulated in 1788 by Scottish geologist James Hutton, who famously observed at Siccar Point that Earth's rocks show "no vestige of a beginning, no prospect of an end." Earth's true age was later measured precisely at 4.54 ± 0.05 billion years through Clair Patterson's 1953 lead isotope analysis of the Canyon Diablo meteorite and early zircon crystals.
The history of macroscopic life is punctuated by the "Big 5" Mass Extinctions, identified in 1982 by Jack Sepkoski and David Raup: the End-Ordovician (~444 Ma), Late Devonian (~372 Ma), End-Permian (~252 Ma), End-Triassic (~201 Ma), and End-Cretaceous (~66 Ma). The End-Permian ("The Great Dying") came closest to extinguishing multicellular life on Earth, when massive basaltic eruptions of the Siberian Traps ignited subsurface coal beds and raised ocean temperatures past 35°C.
Radiometric dating provides absolute dates by measuring the decay of radioactive isotopes at constant, quantum-mechanical half-life rates. Long-lived parent systems such as Uranium-238 to Lead-206 (half-life: 4.47 billion years) and Potassium-40 to Argon-40 (half-life: 1.25 billion years) allow geochronologists to pinpoint key stratigraphic boundaries with sub-permil accuracy.