Radiometric Dating
The time it takes for half of a parent isotope to decay.
What is a half-life?
The LHB occurred about 4.0 to 3.8 billion years ago, when asteroids and these bombarded the inner planets.
What are comets?
A description of the early solar system, when orbits were non-circular and collisions were common.
What is unstable?
These photosynthetic organisms triggered the GOE by releasing oxygen.
What are cyanobacteria?
The concept that life and Earth change together, each influencing the other in a feedback loop.
What is coevolution?
This isotope, with a short half-life, is used to date materials up to 60,000 years old.
What is Carbon-14?
The LHB was likely triggered when the orbits of these two gas giants changed.
What are Jupiter and Saturn?
After the bombardment period, planets settled into these types of stable orbits.
What are (nearly) circular orbits?
Formed on the seafloor as oxygen reacted with dissolved iron; a major piece of evidence for the GOE.
What are Banded Iron Formations (BIFs)?
According to the timeline, the first life appeared around 3.8 bya, nearly this long after Earth formed.
What is 1 billion years (or 800 million years)?
This isotope, with a long half-life, is used to date ancient rocks.
What is Uranium-238?
The LHB is credited with providing this crucial substance to Earth, helping form early oceans.
What is water?
Planets with non-circular, or elliptical, orbits experience big differences in this throughout their year.
What is climate?
These oxidized sedimentary rocks formed after the ocean's iron was used up, showing oxygen entered the atmosphere.
What are red beds?
During the Ordovician extinction, this supercontinent moved over the South Pole, causing global cooling.
What is Gondwana?
The process of determining the absolute age of rocks by measuring isotope decay.
What is radiometric (or radioactive) dating?
This ratio of hydrogen isotopes is analyzed in asteroids to see if they match Earth's "chemical signature" for water.
What is the D/H ratio?
Stability was essential for this substance and this process to persist on Earth.
What are liquid water and life?
Oxygen was this to early simple life, causing major extinctions.
What is toxic?
In the Devonian extinction, the evolution of large land plants caused this type of runoff into the oceans, leading to algal blooms.
What is nutrient runoff?
Scientists dated meteorites, Moon rocks, and these crystals to infer the solar system's age.
What are zircon crystals?
Evidence for the LHB includes impact craters on the Moon, lunar rocks, and these crystals on Earth.
What are zircon crystals?
The solar system settled into its stable state after this major event ended.
What is the Late Heavy Bombardment?
The GOE is placed at this approximate time, based on radiometric dating of BIFs.
What is 2.5 billion years ago (bya)?
The Devonian extinction is a key example of how this (life) can change this (Earth), leading to feedback effects.
What is how life changed Earth?