The bowl-shaped depression at the top of a volcano is a A. <span>a. crater.</span>
Answer: 1- (D)
2- Lithosphere
3- True
4- True
Explanation: Black smokers are generated in the mid oceanic ridges and during the underwater volcanic eruption, which is a hot vent releasing black colored smokes of sulfur from it. They are often associated with the Volcanogenic Massive Sulfide (VMS) deposits.
The lithosphere is the rigid broken plates that are relatively cool and flows over the weaker and viscous asthenosphere layer.
When the groundwater flow intersects the ground level, it forces the water to come out to the surface forming a spring.
The study of changing atmospheric composition along with the ice cores, helps in determing the age upto 800,000 years. But recently, a new discovery has made, in which the ice cores helped in dating back to about 1.5 million years.
Ecological tipping points are the<span> points where environmental problems reach threshold level causing irreversible shifts in the behavior of natural systems. These are also called thresholds where the biodiversity changes.</span>
Answer:
1- Option (D)
2- FALSE
Explanation:
The seafloor spreading takes place because of the divergent plate motion. Alfred Wegener observed this motion of the seafloor and the continents but was not able to explain the main mechanism behind this until the new theory came into the picture. The divergent motion of seafloor and the motion of the continents were explained by the universally accepted theory known as the Plate tectonic theory. This theory was able to explain the mechanism behind this plate motion.
The study of the seafloor spreading provided some pieces of evidence that supported the continental drift theory. They gave a basic idea about how the oceanic plate gets subducted (consumed) at the convergent plate motion that undergoes partial melting at greater depth. As a result of which the magma rises up to the surface on the overriding plates.
The crust represents the outermost layer of the earth. They are of 2 types, namely the oceanic and the continental crust. These crusts when slide past one another in a transform plate boundary, it is neither created nor destroyed. It remains conserved.
Thus, the correct answers are given above and the second statement is false.
