Geologic Timescale Overview

Geologic Timescale

• Eon: the longest geologic subdivision
• Era: "periods" grouped by characteristics
• Epoch: subdivision of periods
• Period: basic unit of geological time, specific rock system produced

Precambrian Eon

• More than 85% of Earth's history (4.6 billion years ago to 540 million years ago)
• Hadean Eon (4.6 billion years ago): solidification of Earth's crust (continental and oceanic)
• Archean Eon (4 billion years ago): evolution of Earth's first life forms

Proterozoic Eon (2.5 Billion Years Ago)

• Appearance of multicellular animals
• Gathering of landmasses to form continents

Phanerozoic Eon

• Paleozoic Era (544 million years ago): explosion of diverse marine life, largest mass extinction of marine organisms
  • Permian Period (298.9 MYA)
  • Pennsylvanian Period (323.2 MYA)
  • Mississippian Period (358.9 MYA)
  • Devonian Period (419.2 MYA)
  • Silurian Period (443.8 MYA)
  • Ordovician Period (485.4 MYA)
  • Cambrian Period (541.0 MYA)
  • Animals in Paleozoic Era: Cockroaches, Jawed Fish
• Mesozoic Era (245 million years ago): beginning of dinosaurs, mammals, birds, and plants (mass extinction)
  • Cretaceous Period (145.0 MYA)
  • Jurassic Period (201.3 MYA)
  • Triassic Period (251.9 MYA)
• Cenozoic Era (65 million years ago - now): most recent era, age of mammals, human evolution
  • Holocene Period (0.01 MYA)
  • Pliocene Period (5.3 MYA)

Types of Rock Stress

• Compression: squeezing rocks together
• Tension: rocks pulled apart
• Shear: forces parallel but moving in opposite directions

Rock Responses to Stress

• Elastic Strain: reversible, returns to original shape when stress removed
• Ductile Strain (plastic deformation): irreversible, rock doesn't return to original shape

Geologic Stress: Folding and Faulting of Rocks

• Stress: force per unit area in a rock
• Strain: deformation (change in shape) in a rock
• Faulting: strain where rocks break
• Folding: strain where rocks bend, curve, and crumple (e.g. monocline, anticline)
• Three Main Fault Types: normal, reverse, strike-slip

Hazards

• Something that may cause harm (death, injury, loss of property)

Risks

• Chance of harm from a hazard

Different Earth Processes

• Geologic
• Hydrometeorological
• Coastal and Marine
• Geologic processes

Earthquakes

• Hazards caused by earthquakes: Tsunami, Liquefaction (soil softening, from solid, and gas to liquid), Landslide, Ground Shaking, Surface Faulting

Volcanic Eruptions

• Hazards caused by Volcanic Eruptions: Pyroclastic Phenomena (mixture of rock fragments, gas, and ash that travels rapidly), Lava, Lahar (volcanic mudflow)
• Pacific Ring of Fire: tectonic belt of earthquakes and active volcanoes

Hydrometeorological Hazards

• Tropical Cyclone types: Tropical Depression (wind pressure lower than 62kph), Tropical Storm (wind pressure 63kph to 117kph), Hurricane (Atlantic Ocean), Typhoon (Pacific Ocean), Cyclone (Indian Ocean)

Monsoon

• A seasonal shift in wind direction and pressure distribution, causing precipitation change
• Northeast Monsoon (Amihan): Cool and dry months of November to February
• Southwest Monsoon (Habagat): months of June to October, extensive cloud development and rainfall

Floods

• Water covering land, affecting millions, destroying houses, and impacting farming
• Damages drinking water, creating diseases

Tornados

• Rapidly rotating columns of air extending from thunderstorm clouds to the ground
• Causes severe damage

Coastal Erosion

• Loss of land along coastlines

Tides

• Gravitational pull between the moon and Earth

Waves

• Formed by wind and storms

Sea Level Rises

• Caused by melting glaciers and icebergs

Crustal Movements

• Motion of Earth's outermost shell

Storm Surge

• Rising of seawater due to atmospheric conditions

Saltwater Intrusion

• Seawater flow into freshwater aquifers

Submersion

• Sediment movement from visible beaches to submerged areas

Disaster Preparedness

• Measures and practices to mitigate disaster effects
• Creating and rehearsing an emergency plan, preparing an emergency kit, conducting trainings
• Disaster Response: Actions taken directly before, during, or after a disaster

Explore the vast history of Earth's geologic timescale, which includes eons, eras, epochs, and periods. From the solidification of Earth's crust in the Hadean Eon to the thriving marine life in the Paleozoic Era, this quiz covers key events and characteristics across different geological timeframes.