Construct a scientific explanation based on evidence from rock strata for how the geologic time scale is used to organize Earth's 4.6-billion-year-old history.

  1. Fossils

    Dino double whammy

    Most scientists think an asteroid helped kill off the dinosaurs. But new calculations suggest that asteroid might have gotten some help from a long series of volcanic eruptions in what is now India.

  2. Earth

    When life exploded

    Life exploded in diversity during the Cambrian Period. Experts are exploring what could account for this sudden change 540 million years ago.

  3. Earth

    Meteorites likely wiped out Earth’s earliest life

    Enormous meteorites appear to have slammed into Earth several times early in its history. Each mega-smashup would have boiled off oceans and obliterated any bit of life.

  4. Planets

    Heavenly research

    Groundbreaking research in astronomy landed four high school seniors spots as finalists in the 2014 Intel Science Talent Search.

  5. Earth

    How Earth’s surface morphs

    Partly melted rock acts like grease to help huge masses of the planet’s surface slip up, around and down.

  6. Space

    The dark side of the universe

    Most of the cosmos is invisible, but that doesn’t stop scientists from searching for it.

  7. Earth

    Deep drilling at sea

    Drilling holes deep into the seafloor unveils the ocean's past and hints at Earth's future.

  8. Fossils

    Did dinosaurs do handstands?

    Enormous dinosaurs might have balanced on their front feet when wading in shallow water.

  9. Space

    A galaxy far, far, far away

    Astronomers have glimpsed some of the most distant galaxies yet found.