Question

Why would the contact between sedimentary rock and high grade metamorphic rock represent an unconformity?

1) metamorphic rocks naturally repulse sediments and inhibit their deposition
2) because sedimentary rocks form at the Earth's surface and metamorphic rocks form deep in the Earth; for sedimentary rocks to be in contact with metamorphic rock, the rock burying the metamorphic rock must have been removed
3) rocks overlying metamorphic rocks are always easily eroded
4) sedimentary rocks have only formed in the very recent geologic past, whereas metamorphic rocks formed mainly in the distant geologic past

Answer 1

The contact between sedimentary rock and high-grade metamorphic rock represents an unconformity because the sedimentary rock is deposited on top of the eroded metamorphic rock, suggesting that the metamorphic rock was uplifted and exposed to erosion before deposition.

Step-by-step explanation:

When sedimentary rock and high-grade metamorphic rock come into contact, it represents an unconformity because the sedimentary rock is deposited directly on top of the eroded metamorphic rock. This suggests that the metamorphic rock was uplifted and exposed to erosion before the sedimentary rock was deposited. This can happen during tectonic activity, where the metamorphic rock is uplifted and then eroded, creating a gap in the geologic record.