Dating and melting
The use of 14C in meteorite dating is solely based on its production by cosmic rays (and for terrestrial samples, with its production in the atmosphere).26Al and some other nuclides not mentioned are also used in this way.
There are well-known methods of finding the ages of some natural objects.After the second half-life has elapsed, yet another 50% of the remaining parent isotope will decay into daughter isotopes, and so on.For all practical purposes, the original isotope is considered extinct after 6 half-life intervals. A small portion of a meteorite is vaporized in the device forming ions.Trees undergo spurts in growth in the spring and summer months while becoming somewhat dormant in the fall and winter months.When a tree is cut down, these periods are exhibited in a cross section of the trunk in the form of rings.Since the days of the great early 20th century polar explorers, scientists have noticed the unbelievably bright blue ponds and streams of meltwater that can form on the glaciers and ice shelves of Antarctica and were even crucial to the recent collapse of one ice shelf.
While most research into Antarctic ice melt has concentrated on the impacts of warming ocean waters that are eating away at the ice from below, a new continent-wide survey shows that these surface meltwater drainage systems are much more prevalent around the continent than was previously thought.
In one paper, the team took a closer look at the system they found on the Nansen Ice Shelf, which was first observed during the Shackleton and Scott expeditions.
The Scott team noted that the “noise of running water from a lot of streams sounded odd after the usual Antarctic silence,” and fell into several of the ponds and streams.
These ions are accelerated in an electric field through collimating slits and subject to a magnetic field which causes the ions to follow a curved path. By adjustment of the strength of the magnetic field and suitable placement of an ion collector, the different isotopes can be measured with precision.
There are some things that affect these measurements.
When those ice shelves are destabilized or crumble, the glaciers behind them flow faster, ferrying more land-bound ice to the ocean and raising global sea levels.