Ice Cores: Part 2 Annual Layers?

Continued from yesterday’s post

IT University of Copenhagen

IT University of Copenhagen (Photo credit: João Ramos)

OK, it took some searching to find people willing to explain just what is being used to calculate the dates they give to ice cores, but the University of Copenhagen was very helpful in describing what’s going on.

Near the surface, where the layers haven’t been squashed by the weight of the snow/ice too badly, it is easy to see differences in the ice.

Each depositional event (e.g. a snow storm) is clearly seen as a distinct layer. Summer and winter snow can often be distinguished by a hard surface, or even sometimes a melt layer, at the top of each summer layer. This is very handy, as the layers in this way can be used for dating purposes, counting from the top how many summer and winter layers there are above a given depth.

Snow layers

Snow layers (Photo credit: brewbooks)

They admit that a single snow storm forms a “distinct layer,” but don’t worry about that too much because Summer “can often be distinguished by a hard surface” each year.  I wonder if they have kept track of freak Summer storms to see if they look like an annual (yearly) layer after a while?

For deep, squashed ice they have to use other ways to determine age.  This gets a bit thick, so I hope I can make sense of this.  Sometimes it seems like they want to make these things so complicated we just have to believe them!

The U. of Copenhagen page sends you on to Ice core dating using stable isotope data to find out what’s going on.  Are your eyes crossed yet?

Alright, here’s how it works.  We know that there are different isotopes (see yesterday’s post for the definition) present in the ice that forms at different temperatures.  So Summer ice has a different amount of these little guys than Winter ice.  From their graph, it looks like there are more isotopes in Summer than Winter.  Since everyone knows there is a Summer once a year and a Winter once a year it is easy to tell one year from another, right?

Oh, wow, look at this:

Thin section of an ice core from Antarctic sea...

Thin section of an ice core from Antarctic sea ice; microscope view under polarized light

As the ice layers get older, the isotopes slowly move around and gradually weaken the annual signal. This process is called diffusion and sets the limit for far back in time annual layers can be identified using δ18O data.

(The delta sign thingy is just the type of isotope they are looking at)  Do you see what they are admitting?  After a certain depth, these atoms get all mixed together and you can’t use them to determine heat/cooling cycles any more.

That’s the end of the page, so now what?  Let’s follow the link Dating using impurity measurements to see how else they figure the age of the ice.

When dating an ice core by counting annual layers, one can use data of any kind that has an annual cycle.

I knew it, I knew it, they are assuming each warming/cooling trend must equal one whole year!

The dust content and the concentration of many chemical impurities in the ice also show seasonal variations and can therefore be used for annual layer counting. The advantage is that the impurities are unaffected by diffusion and can be used to identify annual layers in ice of any age, and that high-resolution measurements of ice impurities produce several parallel data series that can be used for dating, thereby making the annual layer identification process more robust.

They use the dusty layers to determine the age of the ice.  According to this website, there is a distinct layer laid down once a year, no more, no less.

Where does this dust come from?  Well, you’ll have to wait ’til tomorrow!

Then Noah built an altar to honor the Lord. Noah took some of all the clean birds and some of all the clean animals and burned them on the altar as a gift to God.

The Lord smelled these sacrifices, and it pleased him. The Lord said to himself, “I will never again curse the earth as a way to punish people. People are evil from the time they are young, but I will never again destroy every living thing on the earth as I did this time. 

As long as the earth continues, there will always be a time for planting and a time for harvest. There will always be cold and hot, summer and winter, day and night on earth.”  Genesis 8:20-22  Easy-to-read Version

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10 thoughts on “Ice Cores: Part 2 Annual Layers?

  1. Pingback: Ice Cores and the Age of the Earth: Part 1 | Creation Science 4 Kids

  2. Errol Smith

    Hi Cheri, have you also checked out the Wikipedia page on “ice cores”. It shows 2 photos of ice cores from Greenland. These photos avoid complications about isotopes because they use light reflected from the tiny bubbles trapped inside. These ice samples were taken from a depth of about 1800 m (over one mile!) The second photo is a piece of ice 19cm long (about 10 inches) and has 11 distinct white bands, fairly evenly spaced. If you go to the high magnification image of the photos on Wikipedia you can see that each of the white bands is composed of a cluster of smaller white bands of quite variable thickness. However the 11 bands within the 19cm is still a quite clear pattern overall.
    On another easy to read and find article is by H. Riebeek written in 2010: earthobservatory.nasa.gov/Study/Paleoclimatology_IceCores/‎ This shows a photo of shallow ice with the bubbly bands laid down in Summer snow – a direct observation from last few year’s season, and recorded observations of recent decades of summer and winter weather severity of snow. The shallow ice layer broader bands are clearly annual, the bubbly bands being summer and the darker bands winter. Remember that the Arctic and Antarctic winter has very cold long nights, and the summers have very long days – which gives contrasting weather, and ice bubble patterns. The dark and light band patterns steadily become become compressed the deeper one drills – due to the weight of the ice on top of it. This compression is graphed in one of Creation Ministries website links, (Michael Oard, “Do Greenland ice cores show over one hundred thousand years of annual layers?”).
    The maximum depth of ice cores measured so far is over 3km (over 2 miles!). Even in good quality ice cores, the researchers find that the last 200m (600 feet) the layers get distorted due to pressure of variable sideways movements of the ice from pressure of the rock base only 200m away. The researchers do not put much weight on measurements the last 200m. But this still leaves almost 3km of annual ice cores patterns above the disrupted patterns. These bands are all measured and individually counted in recent research, not extrapolated as may have been the case in some early research. Nowadays scientists use automated optical scanners with polarised light, but still check things manually and ideally get several people to give independent assessment at times. Ambiguous bands are noted as such, and hence the numbers of bands measured indicate some variability (+ or -). Recent ice core sites in Antarctica have been chosen because of their relatively constant weather patterns and good quality of clear and horizontal band patterns. Thanks for the opportunity to contribute, and God bless. (P.S. Happy to discuss further.)

    Reply
    1. Cheri-CreationScience4Kids Post author

      I’m kind of wondering why you’re pointing these fascinating details out, Errol? Are you suggesting these layers *must be* annual?
      If so, you must also assume the climate has remained constant for the last 200,000 odd years.
      Those of us who believe in the global flood also see strong evidence for (and have a much easier time explaining) the Ice Age. This would have been a time of most unusal climate variability. You could have had major storms interspersed with warming periods for the entire sunny part of the year. One year could have produced a large number of “annual” layers.
      http://creationscience4kids.com/2012/05/01/the-ice-age-part-2/
      Thank you for taking the time to share with me. It was frustrating trying to discover how scientists determine the age of the lowers sections of ice; no one wanted to talk about it on their site, just wanted people to trust them.

      Reply
  3. Pingback: Cool Facts from Lake Vostok | Creation Science 4 Kids

  4. Pingback: Ice Cores: Part 3 Dust and Ashes | Creation Science 4 Kids

  5. Cheri-CreationScience4Kids Post author

    Well, thank you. This is what I want us all to learn to do. 🙂

    If what we believe is real, we have nothing to fear; God’s world has to back up what He told us. If what we believe is a lie, well, it isn’t, so no worries!

    Reply
    1. Cheri-CreationScience4Kids Post author

      I didn’t contact them, I just went to the webpage.
      The last thing I want to do is have my thinking as inbred as the stuff the other side has to offer. I will post the links I’ve found on AiG et al, but not for my research! 🙂

      Reply
      1. Don Ruhl

        The thing that I was commending was that you went to their source to find out how they reason, rather than listening to someone else tell you how they reason.

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