What determines isotopes for carbon dating are chelsea handler and chubby dating
Another example of yearly layers is the deposition of sediments in lakes, especially the lakes that are located at the end of glaciers.
Rapid melting of the glacier in the summer results in a thick, sandy deposit of sediment.
In 1892, William Thomson (later known as Lord Kelvin) calculated the age of Earth in a systematic fashion (Figure 11.24).
He assumed that the Earth began as a ball of molten rock, which has steadily cooled over time.
For example, layers form within glaciers because there tends to be less snowfall in the summertime, allowing a dark layer of dust to accumulate on top of the winter snow (Figure 11.23).
To study these patterns, scientists drill deep into ice sheets, producing cores hundreds of meters long.
From these assumptions, he calculated that the Earth was 100 million years old.
The resulting layers, called varves, give scientists clues about past climate conditions.Radioactive materials in Earth's interior provide a steady source of heat.Calculations of Earth's age using radioactive decay showed that Earth is actually much older than Thomson calculated.In regions outside the tropics, trees grow more quickly during the warm summer months than during the cooler winter.This pattern of growth results in alternating bands of light-colored, low density "early wood" and dark, high density "late wood".