Plate Tectonics

GRADE 10 SCIENCE First Quarter
EARTH AND SPACE

This photo shows the spectacular view of Mt. Pinatubo during its first major eruption on June, 1991. Keep on reading to learn more about it.

Here are some fascinating facts about the awaken of Mt. Pinatubo:

•   On July 16, 1990, a magnitude 7.8 earthquake struck 60 miles N.E of Mt. Pinatubo shaking and squeezing the Earth’s crust beneath the volcano.
•   On March and April 1991, magma rising from 20 miles beneath Mt. Pinatubo caused small earthquakes and powerful explosions that blasted the volcano.
•    From June 7 – 12, with enough pressure, the first magma from the volcano reached its surface.
•    By June 12, another magma explosion reawaken the first spectacular explosion and major eruption.
•    After the eruption, a lake was formed in the crater, the Pinatubo Lake.

  Visit mountpinatubo.net to show more facts.

To learn about the Mt. Pinatubo eruption, watch the video below:

Geologists believe that Earth’s surface is continuously changing since it was born. It is caused by a force found in the Earth’s interior - the tectonic force. Do you think that this give rise to the formation of volcanoes, mountain ranges, earthquake belt, and other features of the Earth? Tell your idea in the comment section below.

If you look at a map of the world (above), you may notice that some of the continents are like pieces of jigsaw puzzle that fit together. Can you tell which continents/landmasses have this feature? For example, the Northeast coast of Africa closely fits with Southwest coast of Saudi Arabia. Could it be possible that these two landmasses were connected in the past? Did they drift apart and end up separated by the sea? Can a large piece of land move? All these questions will be answered as you explore the lessons.

LESSON 1: PLATE TECTONICS

• The earth's surface is divided or separated into seven large and several small jagged slabs called lithospheric plates which fit together like puzzle pieces. Some plates are submerged in  bodies of water (oceanic) while others have high elevations (continental).  

• The theory that states that lithospheric plates are constantly moving is called the Plate Tectonic Theory. According to this theory, plates move few centimeters per year. But how is this happening?

Explore Plate Tectonics with this INTERACTIVE FLASH
Download the Flash

Resource: https://ees.as.uky.edu

What causes lithospheric plates to move?

TECTONIC FORCE - the force generated beneath the Earth's surface. It generates SEISMIC WAVES that carry SEISMIC ENERGY which cause the shaking of the ground. And YES, earthquake and volcanic activities are some proofs that land can move!

What are Seismic Waves?

Seismic waves are energy carriers released by breaking or rupture of materials underground. These are mechanical waves so they can only travel in the presence of a medium.

• Two types:

• Body waves - seismic waves that travel in the Earth's inner layers.

• Primary and Secondary

• Surface waves - seismic waves that travel in the Earth's surface.

• Rayleigh and Long

Body Waves: PRIMARY VS SECONDARY waves

• Body waves

• P or primary waves

• fastest waves

• travel through solids, liquids, or gases

• compressional wave, material movement is in the same direction as wave movement

• S or secondary waves

• slower than P waves

• travel through solids only

• shear waves - move material perpendicular to wave movement

Why do we have to learn about seismic waves?

•       Data gathered about these waves can be used to track the location of the epicenter.

•       Since these waves travel at different velocity, they do not arrive to the recording station at the same time allowing us to obtain their time difference.

•       The farther the seismic recording station from the epicenter, the greater the difference is  in arrival time of the P and S wave. This will tell us the distance of the earthquake’s focus from the recording station but not the direction.

How do we obtain the direction of the epicenter?

•       TRIANGULATION METHOD – It uses distance information from three seismic stations to locate the earthquake epicenter. On a map, circles are drawn around each seismic station. The radii of the circles are scaled to the estimated distance from the station to the earthquake. The three circles will intersect at one point that locates the earthquake.

Why is it important to locate earthquake epicenters?

•       Locating earthquake epicenters will pinpoint which fault lines are active.

•       Usually, the less active fault line stores great amount of potential energy  that could cause major earthquake once released. Therefore, places near fault lines that remain inactive for a long period of time are due to experience a major earthquake.

LESSON 2: PLATE BOUNDARY

Guide Questions:
1. How do plates move?
2. What happens when they move?

IMPORTANT TERMS TO REMEMBER:

Plates - are large pieces of the upper few hundred kilometers of Earth that move as a single unit as it floats above the mantle. The plates are in constant motion. As they interact along their margins, important geological processes take place, such as the formation of mountain belts, earthquakes, and volcanoes.

Tectonic - refers to the deformation of the crust as a consequence of plate interaction.

Plate boundaries – these are areas where plates meet, collide, pull apart, or scrape each other.

ACTIVITY: PLATE BOUNDARY MODEL

It's better if you do it in group. :)

Three types of plate boundary

There are three types of plate boundary, each related to the movement seen along the boundary.

•          Divergent boundaries are where plates move away from each other.

•          Convergent boundaries are where the plates move towards each other.

•          Transform boundaries are where the plates slide past each other.

See diagrams for each - it is important to remember the names of the boundary types and the motion involved.

In this map, the boundary between two plates include arrows. These arrows signify the direction where plates move. 

Test Your Understanding

Tell whether the boundary between two given plates is Convergent, Divergent, or Transform. Use the map shown above. Write your answer in your notebook.

Example: The plate boundary between Eurasian and Indian plates is CONVERGENT because the arrows between their border are pointing to each other.

  ____________1. Eurasian and Philippine plates
  ____________2. Pacific and Nazca plates 
  ____________3-4. North American and Pacific plates
  ____________5. Eurasian and Indian plates
  ____________6. African and Arabian plates
  ____________7. Cocos and Nazca plates
  ____________8. Indian and African plates
  ____________9. Australian and Antarctic plates
  ____________10. Pacific and Philippine plates