11/4/09

First Ten Minutes: Lock down drill. We considered slipping a piece of white paper half way under the door, but never did. Ms. Meyer didn't know when the drill ended and didn't want to get in trouble so we spend an extra 5 minutes waiting for the drill to end....even though it already had.

Next Half Hour: We took a quiz, which we didn't hand in on Plate Boundaries.

1. The Andes mountains were formed along a subduction plate boundary. It involved the Nazca Plate, an oceanic plate, and the South American Plate, a continental plate. The Nazca plate subducts under the South American plate because it is so much thinner, due to it being an oceanic plate. This then creates a trench and a vent where magma flows up and creates volcanic mountains.

2. The Himalaya mountains were formed along a collision plate boundary. It involved the Eurasian Plate, a continental plate, and the Indian-Australian (or just Indian) plate, which is also a continental plate. The two continental plates of equal thickness collide, push against each other and form mountains.

3. The Mid-Atlantic Ridge is formed along a divergent plate boundary. It formed when the Eurasian and North American plates diverged and created a vent for magma to come up and harden forming underwater rocks and expanding the sea floor. The rocks closest to the ridge are the youngest and the ones farther away are the oldest. Because of the sea floor spreading the Atlantic Ocean is getting bigger.

Last Ten Minutes: We handed in our homework, the Plate tectonic activity packet, and the sea floor spreading rate packet after working on it for a few more minutes.

Remember, test on Tuesday!

Tomorrow's scribe will be Suzie. (spelled with a z or an s, i'm not sure)