Short Answer Type Questions
E. Answer the following questions in brief.
1. Who gave us the theory of Continental Drift?
2. Name the two forces that affect the earth's movements.
3. How does an earthquake occur?
4. What is a dormant volcano?
5. Who invented the seismograph?
Answers
Explanation:
1ans .The theory of continental drift is most associated with the scientist Alfred Wegener. In the early 20th century, Wegener published a paper explaining his theory that the contin
ental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other.
2ans.Horizontal forces and movements are also called as tangential forces. Orogenetic or horizontal forces work in two ways, namely, (i) in opposite direction, and (ii) towards each other. When it operates in opposite directions it is called as 'tensional force
3ans.Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. They don't just slide smoothly; the rocks catch on each other.
4ans.dormant volcano is an active volcano that is not erupting, but supposed to erupt again. An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future.
5ans.
The first seismograph was invented in 132 A.D. by the Chinese astronomer and mathematician Chang Heng. He called it an "earthquake weathercock." Each of the eight dragons had a bronze ball in its mouth
Answer:
Chapter 2 focuses on Earthquakes and Volcanoes.
Lessons included in this chapter:
#4 Earthquakes - The Rolling Earth
#5 Volcanoes
#6 Volcanic Terms
Resources for Teachers can be found under the Chapter #2 Copymaster.
Select from the options on the right to proceed.Why do earthquakes occur? Scientists believed that the movement of the Earth's plates bends and squeezes the rocks at the edges of the plates. Sometimes this bending and squeezing puts great pressure on the rocks. Rocks are somewhat elastic, they can be bent without breaking. Have you ever stretched a rubberband? You know if you increase the tension too much though, the rubberband will snap!! Rock layers act somewhat the same way, if the pressures becomes too great the rock layer will break and move. When this occurs the layers will move along a crack in the Earth's crust called a fault or the release of energy will cause a new faultline to be produced. This rupture of the rocks and the resulting movement causes an earthquake.
This is an aerial photo of the San Andreas fault line in California. The red arrows point to the crack in the crust that is the surface fault. This fault is the boundary between two huge plates, the North American plate and the Pacific plate. The two plates are sliding past each other in opposite directions. This type of plate boundary is called a transverse boundary. A transverse boundary is actually a tear in the Earth's crust. The black arrows represent the directions that the two plates are traveling.
This fault line is perhaps the most studied transverse boundary in the world. Many earthquakes each year occur on the San Andreas fault which runs in California from the Mexico border east of San Diego north to the San Francisco Bay area. The next photo shows the destruction that occurred during the 1971 San Fernando earthquake.
Explanation: