Question

QUESTION 6 When a plate of oceanic lithosphere meets a plate whose leading edge is continental lithosphere along a convergent plate boundary, what is the result? A volcanic island arc, like the modern Aleutian Islands in Alaska. A mountain belt, like the modern Himalayas. Earthquakes, but no volcanism, like the modern San Andreas Fault in California. A continental volcanic arc, like the modern Andes. QUESTION 7 10 The magnetic field of Earth in the geologic past is Click Save and Submit to save and submit. Click Save AllA to save all answers

Answer 1

Answer:

1- Option (4)

Explanation:

When two plates, namely the continental and oceanic plate strike one another, then the denser oceanic plate gets subducted below the less dense continental plate. Due to this subduction zone is formed marked by the deep-sea trenches. The subducting plate undergoes partial melting due and the magma eventually rises up towards the surface of the over-riding plate, forming the continental volcanic arcs. For example, the San Andes mountain which is formed due to the collision between the North American and the Pacific plate.

The earth's core is comprised of denser, molten and hard rocks, that constantly move due to the earth's rotation. As a result of this, the continuous motion of liquid iron initiates electric currents, which again, in turn, produces the earth's magnetic fields. The rotational speed of the earth is directly proportional to the strength of the magnetic field.  

According to the geological evidence, there occurred about 170 magnetic reversals in the past 75-80 million years. In the preceding Matumaya Magnetic Chron, the North Magnetic Pole was oriented towards the Northern Hemisphere.

At present, the strength of the magnetic field of earth is weakening by about 5%. If it continues at this rate then, it may reach zero within some thousands of years.