Introduction To Geology

At Victoria BC (Canada ... used to live there) the tides go through a cycle from two highs and two lows to one high high and one low low and back over a two week period. This is due in part to the geography affecting the tides coming around Vancouver Island in two directions.Enjoy

Hi again Dr Adequate The typical creationist complaint is that this is circular reasoning: rocks to date the fossils that then date the rocks ...... but it is not circular: the first rocks are dated by radiometric methods the second rocks are usually of a type that cannot be dated by radiometric methods, sedimentary rocks, which is where the fossils are found.It's linear:dated rocks → date range for fossils → date range for undated rocksThe layers can also be tracked across the countryside and sometimes found between date-able rocks. And diatoms among others.Enjoy

Excellent as usual.Another visual of ice layers comes from South America: Ice layers introduction on Age Correlations thread

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Paleoclimatology | National Centers for Environmental Information (NCEI) (3)

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(Slide 3) The Quelccaya cap terminates abruptly and spectacularly in a 55 m ice cliff. The annual accumulation layers clearly visible in the photograph are an average of .75 m thick. While snow can fall during any season on the altiplano, most of it (80-90%) arrives between the months of November and April. The distinct seasonality of precipitation at Quelccaya results in the deposition of the dry season dust bands seen in the ice cliff. ...

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Note that they are talking about correlating layers with climate information provided by d¹⁸O. We'll also come across this in other measurement systems. This is the proportion of a "heavy" isotope of oxygen in the atmosphere (¹⁶O is "normal" weight oxygen)

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see Oxygen-16 - Wikipedia (1)
and Oxygen-18 - Wikipedia (2)

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While this series of layers only date back to ~500AD they are important for a couple of reasons: they show visible layers, and they allow calibration of the oxygen isotope ratio (d¹⁸O) as a measure of layers and of climate. These layers also show a period of sever weather that is known from history (the Little Ice A

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And there is more about other ice layer data sources and how the atmosphere isotopes can then be used to estimate ages of deeper layers when they become hard to distinguish.It saddens me to think that we may be losing the Greenland and Antarctic ice fields and the immense bank of data that has not yet been tapped.Enjoy

nothing on page 1 for historical geology from BINGbut #1 for historical geology wikibookEdited by RAZD, : bing