Question

13)the block diagram below represents the formation of an island arc near a plate boundary.
an island arc is located near the boundary between which two tectonic plates?
(1) antarctic plate and indian–australian plate
(2) philippine plate and eurasian plate
(3) scotia plate and south american plate
(4) african plate and north american plate
14)the map below shows a tectonic plate boundary in the atlantic ocean between south america and africa. letters a, b, c, and d represent locations on earths surface.
the most recently formed oceanic crust would be located closest to location
(1) a (2) d (3) c (4) b

Explanation:

Question 13

Step1: Recall Island Arc Formation

Island arcs form at convergent boundaries where an oceanic plate subducts under another oceanic plate (ocean - ocean convergence) or under a continental plate (ocean - continental convergence). We need to identify which of the given plate pairs have such a boundary.

Step2: Analyze Each Option

• Option (1): Antarctic Plate and Indian - Australian Plate: The boundary here is more related to continental - oceanic or other types, not typical for island arc formation from ocean - ocean subduction.
• Option (2): Philippine Plate (oceanic) and Eurasian Plate (continental). The Philippine Plate subducts under the Eurasian Plate, and this type of subduction (ocean - continental) can form an island arc (like the Philippines).
• Option (3): Scotia Plate and South American Plate: The boundary here is a transform or other type, not for island arc formation.
• Option (4): African Plate and North American Plate: This is a divergent boundary (mid - Atlantic ridge - like), not for island arc formation.

Step1: Recall Oceanic Crust Formation

Oceanic crust is formed at mid - ocean ridges (divergent boundaries) through seafloor spreading. The closer a location is to the mid - ocean ridge, the younger (more recently formed) the oceanic crust is.

Step2: Analyze the Map

In the given map, the Mid - Atlantic Ridge is shown. Location C is on the Mid - Atlantic Ridge, location B is a bit away from the ridge, location A is on the South American Plate (continental crust), and location D is on the African Plate (continental crust). So the most recently formed oceanic crust is closest to the mid - ocean ridge, which is location C.

Answer:

(2) Philippine Plate and Eurasian Plate

Question 14