Dating relative rock
The lava flow took place some time after the diorite cooled, was uplifted, and then eroded.
(Hammerhead for scale) [SE]Figure 8.6b Rip-up clasts of shale embedded in Gabriola Formation sandstone, Gabriola Island, B. The pieces of shale were eroded as the sandstone was deposited, so the shale is older than the sandstone.
The simplest and most intuitive way of dating geological features is to look at the relationships between them.
There are a few simple rules for doing this, some of which we’ve already looked at in Chapter 6.
Using this time scale, geologists can place all events of Earth history in order without ever knowing their numerical ages.
Figure 8.6a A xenolith of diorite incorporated into a basalt lava flow, Mauna Kea volcano, Hawaii.
(The near-vertical stripes are blasting drill holes.
The image is about 7 m across.) [SE photo] An unconformity represents an interruption in the process of deposition of sedimentary rocks.
CC BY-SA 1.0], via Wikimedia Commons' src=" alt="" width="474" height="251" srcset=" sizes="(max-width: 474px) 85vw, 474px"/An atom that has different number of neutrons but the same number of protons.
While most properties are based on the number of protons in an element, isotopes can have subtle changes between them, including temperature fractionation and radioactivity.