Science Review!

• Earthquake

  A natural disaster that is a ground shaking caused by a volcanic eruption or by the release of energy along a fault in the Earth's crust
• Tectonic plate movement

  • Plates of Earth are constantly growing at one end, drifting alongside the other plates, and pushing headlong into others
  • There is a buildup of pressure, and rocks are rigid
  • The rapid movement of massive blocks of rock causes earthquakes to release the tension
• Two kinds of earthquakes

  • Volcanic earthquakes
  • Tectonic earthquakes
• Volcanic earthquakes


  • Triggered by the rising magma beneath active volcanoes
  • Less destructive and weaker than tectonic earthquakes
• Tectonic earthquakes

  • Induced by the sudden displacements along fault lines in the Earth's layer
  • Occur as a result of the movements of the crustal plates
  • Cause breaks or cracks called faults that occur at the edge of the tectonic plates
  • Stress mounts along the locked portion of the fault nearer the surface because of the constant motion of the plates
  • The stress increases until the rock breaks and sends out shock waves in the form of earthquakes
• Anatomy of an earthquake

  • Epicenter
  • Focus
  • Fault
  • Seismic waves
• Epicenter

  The area on the surface directly above the focus where the most movement occurs
• Focus

  The underground point of origin where the earthquake occurs
• Fault

  The break in the rock where the movement that has caused the earthquake occurs
• Seismic waves

  The vibrations in rocks that are sent out at great distances from the focus
• Earthquakes send out waves of energy, and their seismic waves cause damage to lives and properties at great distances from the focus
• The "Ring of Fire" consists of 10% of the world's volcanoes and is a horseshoe-shaped area where the Earth's Pacific Plate meets other plates
• Where earthquakes occur in the Philippines

  • Philippine Fault
  • Mindanao Fault
  • East Zambales Fault
  • Labang Fault
  • Philippine Trench
  • Manila Trench
  • Negros-Sala Trench
  • East Lan Trench
• Two ways to describe the strength of an earthquake

  • Intensity
  • Magnitude
• Intensity


  • Based on how people, natural objects, man-made structures, and land surfaces behave and react in areas affected by an earthquake
  • Measured using the Rossi-Forel earthquake intensity scale or the Modified Mercalli scale, from I (weakest) to IX (strongest)
• Magnitude

  • Measures the amount and duration of movements of the ground using a seismograph
  • Registered by a needle connected to the pendulum of the seismograph
  • Measured using the Richter scale, where a magnitude 6 means a strong earthquake and the higher the magnitude, the stronger the earthquake
• Clues used by scientists to predict earthquakes?

  • Occurrence of foreshocks
  • Bulging of the land surface
  • Water level in wells
  • Animal behavior
• In 1995, the Kobe airport in Japan survived an earthquake without damage because it rested on massive spongy feet that acted like giant cushions
• Tsunami


  Huge ocean waves generated by an underwater earthquake, usually occurring in the "Ring of Fire" and can reach heights of 15 meters or more upon reaching the shores
• Earthquake preparedness measures


  • Before an earthquake:
  • Make an emergency plan
  • Discuss with family
  • Prepare emergency supplies
  • Be familiar with exit points
  • Secure heavy furniture
  • Store breakable/dangerous items properly
  • Learn to turn off utilities

  During an earthquake:

  • Stay indoors
  • Cover nose with damp cloth
  • Keep eyes closed

  After an earthquake:

  • Check for damage
  • Turn on radio
  • Stay away from damaged areas
  • Prepare for aftershocks
• How a volcano is formed

  • Regular movements within and beneath the crust form volcanoes
  • Hot core produces heat that moves out and heats the mantle's middle layer
  • Rocks in the mantle become semi-liquid due to extreme heat
  • Magma accumulates in magma chambers and pushes itself above the surface, forming a volcano
• Signs of volcanic eruption

  • Increase in frequency and intensity of earthquakes
  • Ground deformation or bulging
  • Increase in gas release
• Volcanic eruption


  • Caused by shifts in tectonic plates, where one plate is ground down beneath another, melting and producing magma
  • Overlying rock ruptures due to great pressure, resulting in a gentle flow or violent explosion
  • Magma is forced through a crack opening on the surface, releasing lava, ashes, fragments, smoke, gas, and other materials
• What comes out of a volcano

  • Smoke (mixture of gases and water vapor)
  • Lava, rocks, ashes, dust particles, and solid particles
  • Mudflow or lahar (mixture of water and volcanic ash)
• Types of volcanoes

  • Active
  • Inactive
  • Dormant
  • Extinct
• The 1991 eruption of Mt. Pinatubo in the Philippines released large amounts of gases, volcanic ash, mudflow, and rocks, causing widespread destruction and over 800 deaths
• The 1911 eruption of Taal Volcano in the Philippines had a death toll of 1,330
• The 1883 eruption of Mt. Krakatoa in Indonesia caused over 36,000 deaths due to the seismic waves generated
• Beneficial effects of volcanoes

  • Provide natural resources like gas, rocks, and steam
  • Rocks contain minerals like gold, silver, and copper
  • Volcanic ash fertilizes soil, improving crop yields
  • Hot springs provide geothermal energy
  • Volcanic eruptions form new land
• Disaster preparedness measures for volcanic eruptions

  • Before: Be alert, heed warnings, prepare emergency kit, evacuate if necessary

  During: Stay indoors, cover nose, keep eyes closed

  After: Check for damage, turn on radio, stay away from damaged areas, prepare for aftershocks
• Volcanic eruptions cannot be predicted accurately
• Volcanic eruptions can prevent damages to lives and properties
• Precautionary measures should be followed by people before, during, and after a volcanic eruption
• Before a Volcanic Eruption

  1. Be alert for unusual volcanic activity by turning regularly to the latest announcements and bulletins

  2. Heed and follow warnings and instructions issued by authorities

  3. Prepare an emergency kit and other necessities like canned goods, clean water, batteries for flashlights, and clothes. The first-aid kit would be used in case of minor cuts and burns, fever, headache, and diarrhea

  4. Evacuate, if necessary. Do not delay as eruptions can intensify at any time. Evacuation must be calm, orderly, and smoothly. Bring only important items
• During a Volcanic Eruption

  1. Stay indoors

  2. Use a damp cloth to cover your nose as protection from volcanic ash

  3. Keep your eyes closed when air becomes heavy with ash
• After a Volcanic Eruption

  1. When in an evacuation center, wait for instructions to return home

  2. On the way home, do not stay near a river channel or do not cross a bridge while lahar is flowing beneath it

  3. Keep tuned for announcements and bulletins

  4. Remove ash deposits on the roof and other places

  5. Upon returning home, inspect your house for damages. Repair the damages
• Mt. Vesuvius is an example of a volcano
• An earthquake is a natural disaster that is shaking of the Earth's crust caused by a volcanic eruption or by the release of energy along a fault in the crust
• Types of earthquakes

  • Volcanic earthquakes
  • Tectonic earthquakes
• The "Ring of Fire" consists 75% of the world's volcanoes