During this very short week, (only three days of note-taking!), we learned more about earthquakes and the different types of mountains formed on convergent plate boundaries and along ocean ridges.
Monday, November 7: We focused on earthquake magnitude and intensity, the scales used to measure the intensity and destruction of earthquakes, the necessity of seismic stations, seismic belts, and finally, the dangers associated with earthquakes. We learned that the Richter scale measures the magnitude (size) of earthquake waves. The Mercalli scale measures the actual damage caused by an earthquake.
IMPORTANT THINGS TO KNOW: Since the Richter scale moves by 10s, a level 3 earthquake is 10 times bigger than a level 2 earthquake. For the Mercalli scale, the levels of destruction are labeled with Roman numerals, from I to XI. Level I on the scale represents an earthquake that is hardly felt, while a level XI represents an earthquake that leaves very few structures standing.
We then learned about structural failure (buildings are destroyed or even collapse on itself as the ground shakes), land and soil failure (liquid saturation of the soil, which makes it slide), and tsunamis (large ocean waves generated by vertical motions of the seafloor during a quake) that can occur as a result of an earthquake.
We also learned that the two types of vibrations sent out during a quake are p waves (push and pull on rocks), and s waves (cause the ground to move up and down and side to side). Seismic stations record when different waves arrive, and allow the specialists to collect info from three stations (usually) that can be used to pinpoint an epicenter.
Tuesday, November 8: During this class period, each table was given the opportunity to teach one another about the different types of mountains formed along convergent plate boundaries. But before we could teach each other, Mr. Kite gave us vocabulary words that would help us during our reading:
Trench: deep canyon formed on the seafloor when a plate is subducted.
Root: base of a mountain.
Orogeny: mountain building.
Mr. Kite also reminded the class of the three different types of convergent boundaries: Oceanic-Oceanic, Oceanic-Continental, and Continental-Continental.
Here’s what I learned from my table discussion:
- A trench is formed in the crust when one plate subducts into the mantle.
- As the subducted plate melts magma is forced upward, forming a series of volcanic peaks which is sometimes known as an Island Arc Complex.
- The thickness along the island arc that forms a root is displaced, providing the necessary buoyancy for a mountain peak.
- Because it has a low density, continental crust cannot be subducted into the mantle when two plates converge.
- The crust instead becomes highly faulted.
- The crust is broken into thick slabs that push against each other.
- When faulting occurs, mountains are formed.
- Subduction zones and trenches form, which produce major mountain belts.
- Oceanic plates force continental plates upward, marking the beginning of orogeny.
- As subducting plates sink into the mantle, portions of the plates melt.
- The crusts fold and thicken, forming high mountains.
- The melting plates form volcanoes that are fueled by magma.
First, we learned that the rocks on convergent boundaries are warped, faulted, and metamorphic, due to the pressure and heat constantly applied to them. We were given an example of a Non-Convergent Mountain Range, The Mid-Ocean Ridge, and were told that it was formed from warm, rising magma lifting the edge of plates, forming new oceanic crust.
Non-Boundary Mountains: These Mountains are uplifted, and are located nowhere near plate boundaries. The rocks found on these mountains are not warped, morphed, or faulted. This is because they are located above areas where there are warmer spots on the mantle push up on the crust, forming mountains, canyons, and valleys. Fault Block Mountains (movement of the ground at a big fault) and Volcanic (oceanic plate subduction forms volcanoes) are the two types of Non-Boundary Mountains we learned about in class.
*The next day, we focused on our Earthquake & Volcano projects for the duration of the class period (Thursday, November 10).
This unit I learned a bunch of things. Volcanoes, earthquakes, tsunamis, basically anything having to do with how the earth moves.
I learned the anatomy of a volcano and how they form. I learned how there are three different types, each different and unique in their own way.
I also learned the two scales you use to measure earthquakes and how much damage they can actually do.
I learned how Japan suffered on the earthquake of 3/11/11. I learned how the tsunami was actually the matter to make the situation deadly and even more tragic.
I learned how Hawaii came to be, how it’s different from other island groups.
I learned about boundaries, faults, plumes, everything. In total, I learned a whole bunch of things I never even thought about.