Two observed features on Mars appear to lead to contrary geological conclusions—

Question

Two observed features on Mars appear to lead to contrary geological conclusions—the appearance of massive, solitary volcanoes, apparently caused by hot spots under the planet's surface, and the discovery of a long, deep rift valley across the planet. Why are the two features a contradiction?

1. Massive volcanoes should have covered the planet's surface, including the valley, with dust and ash, but the valley remains as a major feature. 2. Single massive volcanoes indicate hot-spot volcanism with no plate tectonic motion, whereas a rift valley suggests otherwise. 3. Volcanoes suggest a molten inner planet, whereas a rift valley suggests the presence of a solid core. 4. Ancient volcanoes show no sign of erosion by water, whereas the valley suggests prolonged rainfall and erosion.

Explanation / Answer

The answer is 2

the apparent contradiction is that single massive volcanoes generally iindicate the non tectonic motion whereas the rift valley one suggests.

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