A theodolite works by combining optical plummets (or plumb bobs), a spirit and graduated circles to find vertical and horizontal angles in surveying. An optical plummet ensures the theodolite is place as close to exactly vertical above the survey point.
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Answer:
a. granite, andesite, basalt
Explanation:
There are three basic different types of magma: rhyolithic, andesitic, and basaltic. These three types of magma have different properties which differs them from one another, and which cause different types of eruptions. The rhyolithic (granite) magma has very high viscosity. This magma is the thickest, managing to trap gases in it, and because of it it causes highly explosive eruptions. The andesitic magma is moderate in viscosity, and it has explosive eruptions, but also has lava flows that are relatively slow, so it is very unpredictable what kind of an eruption will the volcano have. The basaltic magma is the least viscous. This means that the eruptions of these volcanoes are not explosive, but instead they produce thin lava flows that cover the surrounding area.
The rate of pacific plate motion is 7 centimeters per year.
<h3>Movement of pacific plate</h3>
The rate of pacific plate motion is seven centimeters which is equals to 2.75 inches per year i.e. about the rate at which fingernails grow. The main reason behind the movement of Pacific Plate is due to sea floor spreading from the East Pacific Rise (divergent margin) in the Gulf of California.
While on the other hand, the North American Plate moved to the west and north west due to sea floor spreading from the Mid Atlantic Ridge (divergent margin) so we can conclude that the rate of pacific plate motion is 7 centimeters per year.
Learn more about plate movement here: brainly.com/question/18219355
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