Historical Geology

Use this for “An ash bed is 252 Ma and a lava flow 50 m below it is 254.5 Ma. How fast did the beds pile up, and how old is a fossil bed 30 m up?”

Use this for “A dike cuts a sill. Which principle says which is older?”

Use this for “Flat sandstone lies on eroded granite. What kind of unconformity is it?”

Use this for “Samples of one granite plot on a line of slope 0.0145 on a graph of ⁸⁷Sr/⁸⁶Sr against ⁸⁷Rb/⁸⁶Sr. How old is the granite?”

Use this for “A lava flow holds 0.01 argon-40 atom for every potassium-40 atom. How long ago did it cool?”

Use this for “Charcoal from a hearth gives 3.4 decays per minute per gram, and living carbon gives 13.6. How old is the charcoal?”

Use this for “Dinosaur footprints in mudstone and a snail shell in limestone: which is a body fossil and which a trace fossil?”

Use this for “4 billion years ago the Sun was dimmer. With today’s albedo of 0.3 and no greenhouse effect, how cold was Earth?”

Use this for “The Great Oxidation Event left the first red beds. In which eon did it happen?”