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Contents of 7.5 How do you recognize gaps in the rock record?

• Unconformities are former land or seafloor surfaces between rock layers that represent time intervals not recorded in the local rock record.
• Angular unconformities separate sedimentary or volcanic rocks inclined at different angles. The time of tilting and erosion are not recorded in the geologic record.
• Disconformities separate sedimentary or volcanic rocks at the same angles but are separated by an irregular erosion surface that indicates a break in the deposition or erosion of the older rocks.
• Nonconformities separate sedimentary or volcanic rocks from underlying plutonic-igneous or metamorphic rocks. The time taken to erode overlying materials until sedimentation is not part of the geologic record.

7.5 How do you recognize gaps in the rock record?