Question

1. explore2_the snake river plain extends across southern idaho and is labeled “srp” in the map. yellowstone national park is located at the northwestern tip of this plain and is well known for its geysers, hot basins, and hot springs. regions of the snake river plain show evidence of ancient lava flows. analysis of the ages of volcanic rocks from these lava flows reveals that rocks from different regions are older than others. the map contains ages of volcanic rocks from seven different regions listed in millions of years (abbreviated ma for mega - annum). each region corresponds to a different volcano that originally stood in that region. what can you infer from this information about how those ancient volcanoes formed? they formed during subduction at a continental plate boundary. they formed from oceanic plates moving apart at a divergent boundary. they formed from magma rising up from a hot spot and breaking through the cru they formed as the result of subduction during oceanic plate - continental plate convergence.

Explanation:

1. Analyze the first option: Subduction at a continental - continental plate boundary typically forms mountain ranges like the Himalayas, not the pattern of volcanoes with different - aged rocks along a plain. So this option is incorrect.
2. Analyze the second option: Divergent boundaries in the ocean (mid - ocean ridges) form new oceanic crust, and the pattern of volcanoes here doesn't match the divergent boundary volcano formation (which is more about seafloor spreading and not a linear chain with age progression on land). So this option is incorrect.
3. Analyze the third option: A hot - spot volcano forms a chain of volcanoes as the tectonic plate moves over a stationary hot spot. The older rocks would be farther from the current hot - spot (Yellowstone, which is at the northwestern tip). The Snake River Plain has volcanoes with different ages, which fits the hot - spot model where the plate moves and new volcanoes form over the hot spot, and older ones are left behind as the plate moves.
4. Analyze the fourth option: Subduction at an oceanic - continental plate boundary forms a volcanic arc (like the Andes or Cascades), which is a different pattern than the linear chain with age progression seen here. So this option is incorrect.

Answer:

C. They formed from magma rising up from a hot spot and breaking through the crust