Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
|  | geological feature |  | force that creates the feature |
| --- | --- | --- | --- |
| A(n) | mountain | is formed by | plate tectonics; volcanoes |
| A(n) | plateau | is formed by | erosion from running water; glacial erosion; upswelling of magma; lava flows |
| A(n) | valley | is formed by | erosion from running water; glacial erosion |
| A(n) | bay | is formed by | continental drift; erosion from running water; glacial erosion |
| A(n) | volcano | is formed by | a rupture in the earth's crust |
| A(n) | ocean ridge | is formed by | plate tectonics |
| A(n) | canyon; gorge | is formed by | erosion from running water |
| A(n) | dune | is formed by | wind; water movement |
| A(n) | cliff | is formed by | erosion; weathering |
| A(n) | cave | is formed by | weathering |
| A(n) | fjord | is formed by | glacial erosion |
| A(n) | gulch | is formed by | erosion |
| A(n) | gully | is formed by | erosion from running water |
| A(n) | ravine | is formed by | erosion |
| A(n) | crater lake | is formed by | volcanic explosion |
| A(n) | glacial lake | is formed by | glacial erosion |
| A(n) | tectonic lake | is formed by | tectonic uplift of mountain ranges |
| A(n) | floodplain | is formed by | flooding |
Question:
How is a volcano formed? Select the correct choice to answer the question or fill in the blank.
Choices:
(A) a rupture in the earth's crust
(B) erosion
(C) glacier
(D) wind
Answer:
(A) a rupture in the earth's crust