Isochron Diagrams

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On the control part of the graph select the Rb/Sr option.

Rember that the Half-life of Rb-87 is 48.8 Billion Years. Note that the scale on the horizontal axis is now 10 times greater than the vertical axis.

Move the slider and watch the slope of the isochron change over time.

You can also type numbers directly into the text box displaying the slope. Press the return key to activate any typed-in change.

Go ahead and complete the table.
Isochron Slope Age in MILLION of years Geologic Event
0.002

1.
Dinosaurs roamed the earth
0.0077

2.
First evidence of abundant fossils
0.0362

3.
Proterozoic Era begins
0.0582

4.
Oldest radiometrically dated Earth rock
0.0668

5.
Earth's age, inferred from meteorites

1. - 140

2. - 540
3. - 2500
4. - 3980
5. - 4550

Dinosaurs roamed the earth- 140

How old is granite in millions of years from the Scottish Highlands?

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6. The first joke was told.

To understand isochron diagrams, let's start with some basic definitions.

An isochron is a graphical representation that shows the relationship between the ratio of two isotopes in a sample and their age. It is commonly used in geochronology to determine the age of rocks and minerals.

On the control part of the graph, you need to select the Rb/Sr option. Rb stands for rubidium and Sr stands for strontium. These two isotopes are commonly used in isochron dating methods.

The half-life of Rb-87 is 48.8 billion years. This means that it takes 48.8 billion years for half of the Rb-87 in a sample to decay into other isotopes. Knowing the half-life is important because it allows us to calculate the age of the sample based on the ratio of Rb-87 to its decay product, Sr-87.

The scale on the horizontal axis is 10 times greater than the vertical axis. This means that the horizontal axis represents longer periods of time compared to the vertical axis.

By moving the slider, you can observe how the slope of the isochron changes over time. The slope of the isochron is directly related to the age of the sample. As time passes and more decay occurs, the ratio of Rb-87 to Sr-87 changes, resulting in a change in the slope of the isochron line.

You can also directly type numbers into the text box displaying the slope. Pressing the return key will activate any changes you make.

Now, you are asked to complete the table by determining the isochron slope and the corresponding age in millions of years for various geologic events.

To do this, observe the isochron line on the graph and determine the slope of each segment corresponding to the given events. Enter the calculated slope values into the table.

Once you have the slope values, use the equation of the line, which relates the slope to the age of the sample. Multiply the slope by the half-life of Rb-87 (48.8 billion years) and convert it into millions of years by dividing by 1,000.

Fill in the calculated age in millions of years in the respective column of the table for each geologic event.

Remember to refer to the isochron diagram and follow the instructions provided to complete the table accurately.