Question 139208 • CV Q4 M/J Science 3 Adv 2002110 Compacted Review of Grade.7.Life for SSA Prep
A cross-cutting feature, such as a fault or an igneous intrusion, formed after the rock layers it cuts through, so it is younger than the surrounding rock. When older material is eroded and sediment is later deposited over it, some geologic time is missing from the record; this gap is an unconformity. Lava forming at the surface is an extrusion, not the definition of an unconformity, and intrusions and extrusions are igneous rather than sedimentary formations.
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