Question

1. base your answer to the following question on the map below which shows mid-ocean ridges and trenches in the pacific ocean. specific areas a, b, c, and d are indicated by shaded rectangles.

movement of the crustal plates shown in the diagram is most likely caused by
(1) the revolution of the earth
(2) the erosion of the earths crust
(3) convection currents in the earths mantle
(4) shifting of the earths magnetic poles

1. earths internal heat is the primary source of energy that

(1) melts glacial ice at lower altitudes
(2) moves the lithospheric plates
(3) warms the lower troposphere
(4) pollutes deep groundwater with radioactivity

1. the mariana trench is earths deepest oceanic trench. this trench formed as the pacific plate was

(1) overriding the philippine plate
(2) subducting under the eurasian plate
(3) subducting under the philippine plate
(4) overriding the eurasian plate

Explanation:

Question 15

To determine the cause of crustal plate movement, we analyze each option:

• Option (1): Earth's revolution (orbiting the Sun) doesn't cause plate movement. Eliminate.
• Option (2): Erosion affects the crust's surface, not plate tectonics. Eliminate.
• Option (3): Convection currents in the mantle transfer heat, creating forces that move lithospheric plates. This matches plate tectonics theory.
• Option (4): Magnetic pole shifts don't drive plate movement. Eliminate.

Analyzing the role of Earth's internal heat:

• Option (1): Glacial ice melting at lower altitudes is due to surface heating (e.g., solar radiation), not internal heat. Eliminate.
• Option (2): Internal heat drives mantle convection, which moves lithospheric plates. This is consistent with plate tectonics.
• Option (3): The troposphere is warmed by solar radiation and surface heat, not internal heat. Eliminate.
• Option (4): Radioactive pollution of groundwater isn't a primary role of internal heat. Eliminate.

For the Mariana Trench formation:

• Oceanic trenches form at subduction zones where an oceanic plate subducts (dives) under another plate. The Pacific Plate subducts under the Philippine Plate at the Mariana Trench.
• Option (1): Overriding (not subducting) doesn't form trenches. Eliminate.
• Option (2): The Mariana Trench involves the Pacific and Philippine Plates, not Eurasian. Eliminate.
• Option (3): Correct, as Pacific Plate subducts under Philippine Plate.
• Option (4): Overriding and Eurasian Plate are incorrect. Eliminate.

Answer:

(3) convection currents in the Earth's mantle

Question 16