Question

during the last supercontinent cycle, antarctica was connected to south america (see image above right). when they separated, a powerful ocean current formed around antarctica. this current isolated the continent from the warming effects of other currents.

1. why did antarctica get colder when it was separated from south america?

a. the south pole gets less sunlight, so it is colder
b. the ocean current that formed around antarctica blocked warm water from reaching it
c. a glacier rolled over onto antarctica
antarctica gradually cooled and froze. north america and south america were joined together by the creation of the isthmus of panama, about 5 million years ago (see image to the right). before that, tropical ocean water flowed directly between the atlantic and pacific oceans. when the ocean circulation patterns changed, a period of glaciation (formation of glaciers) set in. these changes also impacted the distribution and evolution of marine organisms (ocean life).

1. according to the text, what is an isthmus?

a. a channel that water flows through
b. a land bridge that connects two continents
c. a frozen pathway

Explanation:

For the first question, when Antarctica separated from South America, a powerful ocean - current formed around Antarctica which blocked warm water from reaching it, causing it to get colder. For the second question, the text mentions that North and South America were joined by the creation of the Isthmus of Panama, which is a land - bridge connecting two continents.

Answer:

1. B. The ocean current that formed around Antarctica blocked warm water from reaching it
2. B. A land bridge that connects two continents