Science

• Earthquake


  Sudden movement or vibration of the Earth's rocky outer layer
• Earthquake


  • Caused when rock masses suddenly shift in position
  • Energy stored in rock masses is transmitted onto the surface in the form of seismic waves
• Crustal plates


  • Outer shell of the Earth
  • Surface along which crust moves is called a fault line
• Seismometer


  • Instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions and explosions
  • Usually combined with a timing device and a recording device to form a seismograph
• Magnitude


  Quantitative measure of an earthquake's strength in terms of energy released
• Intensity

  • Qualitative measure of an earthquake's severity in terms of damages caused at a particular location
  • Generally higher near the epicenter
• Larger the earthquake


  Greater the intensity
• Focus


  Actual location where fault movement begins, below the Earth's surface
• Epicenter


  Point on the land surface directly above the focus
• Types of natural earthquakes

  • Tectonic earthquakes
  • Volcanic earthquakes
• Tectonic earthquakes


  Produced by sudden movement along faults and plate boundaries
• Volcanic earthquakes


  Produced by the movement of magma beneath volcanoes
• Tectonic earthquakes


  Cause collapse of different structures
• Volcanic earthquakes


  Cause explosions
• Volcanic earthquake


  • Caused by movement of magma beneath the Earth's surface
  • Pressure changes where the rock around the magma has experienced stress
  • Stress can cause the rock to break or move
• Scientists cannot predict earthquakes, but can point out where fault lines are to know where earthquakes are likely to occur
• The largest earthquake ever recorded was in Chile in 1960, measuring 9.6 on the Richter scale
• The largest earthquake in the US was a 9.2 magnitude in Alaska in 1964
• Earthquakes can cause tsunamis
• Movement of tectonic plates forms large mountain ranges like the Himalayas and the Andes
• Earthquakes can happen in any kind of weather
• Plants and trees in countries like the United States, Korea, or Japan are different from what we have in the Philippines
• Changes occur in plants in different times of the year in countries with four seasons
• The Philippines has only two seasons: wet and dry
• The earth moves in two ways: rotation and revolution
• Earth's rotation


  1. Movement of the earth on its axis

  2. The sun appears to rise in the east and set in the west

  3. The earth rotates counterclockwise from west to east

  4. Causes day and night
• Rotation


  The movement of the earth on its axis
• One complete rotation of the earth is defined as a day, which takes 23 hours 56 minutes and 4.2 seconds
• Revolution


  The movement of the earth around the sun
• The earth revolves around the sun in a counterclockwise direction, taking 365 and one-quarter days
• To keep the calendar in sync with the earth's revolution, a leap year with 366 days is used every four years
• Earth's orbit


  • Not a perfect circle, but a slightly flattened circle (ellipse)
  • The earth's farthest point from the sun is called aphelion
  • The earth's nearest point from the sun is called perihelion
• The earth's axis remains fixed in space as it orbits the sun
• The tilt of the earth's axis at 23 degrees causes the four seasons in some countries
• Seasons in the northern hemisphere

  1. Summer (June-August)

  2. Autumn/Fall (September-November)

  3. Winter (December-February)

  4. Spring (March-May)
• The Philippines and other equatorial countries experience only the wet and dry seasons, not the four seasons