# Reading a point from a curve or linePractice Problems

The problems below walk you through the steps for reading points from a line. You can click on any of the graphs to open a bigger version or you can click the link under the graph to download a pdf of the graph for printing! Please try to complete these activities without peeking at the answers - this will help you when you get to the quiz at the end!

Geologists use information about the ratio of radioactive (parent) atoms to their decay product (daughter) atoms to understand the age of igneous, metamorphic and sedimentary rocks. The behavior of all radioactive elements is the same and the time it takes for one-half of the parent atoms to decay to daughter atoms is called the half-life. The graph below shows a plot of Daughter/Parent Ratio to Half-lives elapsed showing how geologists use isotopes to determine the age of rocks. This is a general plot that works for any isotope system. Use this plot to answer the questions below about reading points from a line.

Click to enlarge, or download a PDF (Acrobat (PDF) 25kB Jun25 10)

## Floods and Flood Frequency

Geologists keep track of the "stage" or height of floods every year and use that data to predict the probability that a flood will occur in any given year. The plot below is called a flood frequency curve, constructed from data collected over a number of years (sometimes as many as 100 -200 years. The plot below represents data from a hypothetical river for which we had 69 years of data. The probability is reported as something called a Recurrence interval and is reported in "years". Use the plot below to answer the following questions.

## Climate Change and Greenhouse Gases

Geoscientists use information gathered from the atmosphere and ice cores to understand long-term climate change and the role of greenhouse gases. On top of Mauna Loa, in Hawaii, a weather station collects information about the CO2 content of our atmosphere - Mauna Loa is far above the immediate influence of CO2 emissions from traffic because it is nearly 4170 meters (about 13680 feet) above sea level (see USGS Mauna Loa Volcano). The data collected between 1987 and 2006 is presented below in graphical form. Use this graph (you can download a larger version as a PDF to print) to answer the questions below. Note that the data shows a cyclical pattern that is associated with seasons (e.g., winter and summer) but that the trend shows that CO2 concentrations in our atmosphere are generally increasing.

## TAKE THE QUIZ!!

I think I've mastered plotting points and I am ready to take the quiz!

This link takes you to WAMAP. If your instructor has not given you instructions about wamap, you may not have to take the quiz.

If you still need help, you can go back to the explanation page or look at some of the links below.