History of the Earth

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Across
  1. 3. Began 252 million years ago and lasted until 66 million years ago; the era spanned a large amount of time, divided into the Triassic, Jurassic, and Cretaceous periods.
  2. 5. The region where liquid water neither freezes nor evaporates but can remain as a liquid at the surface.
  3. 7. A pattern that forms in the mantle layer when warm molten rock material rises, cools, and eventually sinks down, causing the movement of plates.
  4. 8. A thin shell on the outside of Earth, accounting for less than 1% of Earth's mass and volume.
  5. 10. Igneous rock that forms at Earth’s surface and cools very quickly, meaning crystals do not grow much before the rock cools (fine-grained texture).
  6. 13. A solid combination of minerals or mineral materials.
  7. 15. The oldest eon (4.5–4.0 billion years ago); characterized by a partially molten surface, volcanism, and asteroid impacts.
  8. 18. A single continent formed when the continents were once joined.
  9. 22. Forces that shape the surface by building up mountains and other land areas (processes include deposition, landslides, volcanic eruptions, and floods).
  10. 24. A division of geologic time lasting millions of years.
  11. 27. A highly viscous, mechanically weak and ductility deforming region of the upper mantle of the Earth, lying below the lithosphere.
  12. 29. Regions where two tectonic plates are moving toward each other.
  13. 30. Magma that flows out of volcanoes.
  14. 31. The current period we are in, characterized by several periods of glaciation ("ice ages").
  15. 34. A division of geologic time lasting tens of million years (the smallest division mentioned).
  16. 36. Consists of 78% nitrogen, 21% oxygen, and 1% other gases; affects Earth's long-term climate and local weather, and shields us from harmful radiation and meteoroids.
  17. 38. A division of geologic time lasting hundreds of millions of years.
  18. 40. Regions where two plates slide horizontally past each other.
  19. 45. A division of geologic time lasting tens to hundreds of millions of years.
  20. 46. Huge pieces of crust and rigid upper mantle that fit together at their edges to cover Earth's surface.
  21. 48. Plates formed by convergent plate boundaries, felsic in nature, dominated by granitic rock rich in silica, aluminum, sodium, and potassium.
  22. 49. The innermost geologic layer of our planet, made of mostly iron (Fe) and nickel (Ni), and maintains a temperature of 9,392°F.
  23. 51. A dating method used by archeologists for objects generally younger than 50,000 years (like trees, plants, animal remains, or human artifacts) but not typically used by geologists to determine the age of rocks.
  24. 52. Causes compass needles to point to the North Pole. It pushes eastwards on the inner core (causing it to spin faster than the Earth) and pushes in the opposite direction on the liquid outer core (creating a westward motion).
Down
  1. 1. The correlation and classification of rock strata, used to establish a geologic time scale.
  2. 2. The physical and chemical process that breaks down rocks
  3. 3. Inorganic substances that occur naturally; they are naturally occurring inorganic solids with a crystal structure and a homogeneous chemical composition, and are considered the building blocks of rocks.
  4. 4. States that intrusions are younger than the rock it cuts across; this also applies to faults.
  5. 6. The principle that sedimentary rocks are deposited in horizontal (or nearly horizontal) layers.
  6. 9. A basic law of geochronology stating that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom.
  7. 11. The largest division of geologic time (1 billion years +).
  8. 12. Plates formed by divergent plate boundaries, mafic in nature, composed of basalt rock and its coarse-grained equivalent, gabbro, rich in iron, magnesium, and calcium.
  9. 14. Began about 66 million years ago and extends to the present; the time during which the continents assumed their modern configuration and geographic positions and Earth’s flora and fauna evolved toward those of the present.
  10. 16. Rock that forms when molten material cools and solidifies either inside Earth or at the surface.
  11. 17. Regions where two tectonic plates are moving apart from each other.
  12. 19. A method that gives a better understanding of the geologic events in Earth’s history but does not allow scientists to determine the exact age of rocks.
  13. 20. The layer between the inner core and mantle, mostly composed of molten iron and nickel at 8,000–10,000°F.
  14. 21. Rock that forms over time as sediment is squeezed and cemented together.
  15. 23. Igneous rock that forms underground from hardened magma and cools slowly, allowing crystals to grow large (coarse-grained texture).
  16. 25. A geological eon spanning the time from the appearance of oxygen in Earth’s atmosphere to just before the proliferation of complex life on the Earth.
  17. 26. Forces that slowly wear away mountains and eventually every other feature on Earth's surface (processes include weathering, erosion, landslides, volcanic eruptions, earthquakes, and floods).
  18. 28. Started 542 million years ago with the emergence of complex life forms and ended 251 million years ago with the largest mass extinction the world has ever experienced.
  19. 32. The cool, rigid layer that is linked to the tectonic plates and behaves elastically on time scales of thousands of years or greater.
  20. 33. Discoveries of this phenomenon beginning in the mid-1950s supported Alfred Wegener's hypothesis of continental drift.
  21. 35. What is caused by the outer and inner core.
  22. 37. Rock that has been changed (transformed) by temperature, pressure, or chemical reactions with hot water.
  23. 38. Carries away particles produced by weathering.
  24. 39. A layer inside a planetary body bounded below by a core and above by a crust; made of rock or ices, and generally the largest and most massive layer of the planetary body.
  25. 41. A series of processes in which rocks continuously change from one type to another, caused by forces within Earth and at the surface.
  26. 42. A mixture of molten rock and gases, including water vapor, which forms underground in the earth's mantle.
  27. 43. The idea that geologic processes that operate today also operated in the past.
  28. 44. The hypothesis that the Earth’s continents have moved over geologic time relative to each other, thus appearing to have "drifted" across the ocean bed.
  29. 47. Result when tectonic plates grind past one another, ride up over one another, collide to make mountains, or split and separate.
  30. 50. A process that occurs at convergent boundaries where the denser plate eventually descends below the less dense plate.