Earth Science Pointers

• Earth science


  The name for all the sciences that collectively seek to understand Earth and its neighbors in space, including geology, oceanography, meteorology, and astronomy
• The Earth is older than previously thought
• 300 years ago, geologists thought the Earth was about 6,000 years old
• Later, geologists discovered rocks that were formed 40 million years ago
• Today, scientists claim the Earth is between 4 and 5 billion years old
• How scientists determined the Earth's age


  1. Study of rocks

  2. Measuring changes in rocks over time

  3. Studying the order of rock layers (Law of Superposition)

  4. Radioactive dating
• Law of Superposition


  In undisturbed sedimentary rocks, each layer is younger than the layer below it and older than the layer above it
• Igneous rocks and volcanic rocks make it more difficult to determine the age of rocks
• Radioactive dating


  A reliable method to tell the Earth's age by measuring the amounts of radioactive elements and their decay products in rock samples
• Some rocks have been found to be 5 billion years old using radioactive dating
• Fossils


  Hardened remains or imprints of organisms that lived a very long time ago
• Fossils


  • They provide records of the past, including when glaciers or seas covered the land, when volcanoes erupted, when mountains were pushed up, and the kinds of living things that existed millions of years ago
• Types of fossils


  • Footprints
  • Impressions in hardened materials like cement
  • Petrified or changed into rock
  • Whole bodies or skeletons preserved in materials like ice and amber
• Fossils reveal the sizes, shapes, appearances, habits, and habitats of living things from long ago
• Geologic time scale


  The division of the story of living creatures into eras, periods, and epochs based on the dominant life forms that existed
• Geologic eras


  • Precambrian
  • Paleozoic
  • Mesozoic
  • Cenozoic
• Precambrian era


  • Lasted from the beginning of the Earth to about 600 million years ago
  • Primitive organisms existed but left few fossils
  • Mostly igneous and metamorphic rocks
• Paleozoic era


  • Many marine invertebrate fossils found
  • First animals adapted to breathe air and land plants developed
  • Reptiles appeared towards the end
• Mesozoic era


  • Continents formed and drifted apart
  • Dinosaurs were the dominant life forms
  • Reptiles survived while dinosaurs died out
• Cenozoic era


  • Warm-blooded animals like mammals and birds appeared
  • Glaciation occurred in the Northern Hemisphere
  • Earliest human records like stone tools
• The Earth is not a perfect sphere due to its equatorial bulge and irregular surface with mountains and valleys
• Oblate spheroid


  The geometric form closest to the actual contours of the Earth, as computed by J.P. Hayford in 1910
• How Eratosthenes measured the Earth's circumference

  1. Measured the angle of the sun's rays at two locations 800 km apart

  2. Calculated the circumference based on the angle difference
• Eratosthenes' calculation of the Earth's circumference was within a few hundred kilometers of the modern value
• Latitude


  Lines drawn east-west around the Earth, measured from 0° at the equator to 90° at the poles
• Longitude


  Lines drawn north-south from pole to pole, with the prime meridian at 0° passing through Greenwich, England
• The International Date Line is at 180° longitude, directly opposite the prime meridian
• Map scale


  Enables determining the distance between places on a map compared to the actual distance on Earth's surface
• Globes are spherical models of the Earth that show the sizes, shapes, and locations of continents and bodies of water
• International Date Line


  Line where east and west longitude lines meet at 180° meridian. If you cross this line going west, you add one day.
• The International Date Line is directly opposite Greenwich on the other side of the Earth
• West longitude


  Points west of the prime meridian
• East longitude


  Points east of the prime meridian
• Map


  A drawing of the earth, or part of the earth on a flat surface
• Globe


  A spherical model of the Earth that shows the sizes, shapes, and locations of all continents and bodies of water
• Map scale


  Enables us to tell the distance between places on a map and compare it to actual distance on Earth's surface
• Map features


  • Roads, rivers, national parks, national highways
• Map symbols


  Drawings that stand for real places or things, explained in the map legend
• Topographic map


  Shows roads, cities, mountains, hills, and rivers using contour lines to show relief
• Earth's layers


  Crust, mantle, outer core, inner core