Question

it is oceanic crust uplifted by a large thrust fault.
☑ it formed from flood basalts associated with a hot spot.
it formed as continental crust detached from the continent at a transform plate boundary.
it formed in an island arc as the volcanic islands fused together.
correct! nice job.
explain how sea floor features form. 5 of 5
back to south america, where we can see both coasts near the southern tip of the continent, with the atlantic ocean to the east and the pacific ocean to the west. which of the following statements is true?
there are oceanic plateaus just offshore in both oceans.
there is a passive continental margin on the eastern side of south america.
there is an ocean trench along the atlantic coastline.
there is an island arc just off the west coast of south america.

Explanation:

To determine the correct statement, we analyze each option:

1. "There are oceanic plateaus just offshore in both oceans": Oceanic plateaus form from flood basalts (like the Ontong Java Plateau) or other large - scale volcanic events. The Atlantic and Pacific off South America don't both have prominent oceanic plateaus offshore in the described region.
2. "There is a passive continental margin on the eastern side of South America": A passive continental margin occurs at a divergent plate boundary (where plates move apart) and is characterized by a lack of active tectonic activity (like subduction or transform faults) along the margin. The eastern coast of South America is along the South American - African divergent boundary (part of the Mid - Atlantic Ridge system), so it is a passive continental margin.
3. "There is an ocean trench along the Atlantic coastline": Ocean trenches form at convergent plate boundaries where one plate subducts under another. The Atlantic coast of South America is a passive margin (divergent), so there is no ocean trench there. Ocean trenches (like the Peru - Chile Trench) are along the western (Pacific) coast where subduction occurs.
4. "There is an island arc just off the west coast of South America": An island arc forms at a convergent boundary where an oceanic plate subducts under another oceanic plate (e.g., the Japanese island arc). The west coast of South America has a continental - oceanic convergent boundary (the Nazca plate subducts under the South American plate), forming a continental volcanic arc (the Andes Mountains), not an island arc.

Answer:

B. There is a passive continental margin on the eastern side of South America