## Graphs with two axes can also be called:

Linear plots/graphs
Binary/bivariate plots/graphs
Cartesian plots

# How can I use graphs in the geosciences?An overview of the use of plots

## Graphs as a way to visualize numerical data

Atmospheric Carbon Dioxide levels measured in the atmosphere above Mauna Loa, Hawaii (modified from Keeling and Whorf, 2003). Click on image for larger version

Advances in technology have meant that geoscientists can collect large volumes of numerical data in short periods of time - from geochemical analyses of rocks, to measurements of angles, to the composition of the atmosphere. With all those numbers (like the table of carbon dioxide measurements to the right), how can we tell what the data is telling us? One way that geoscientists process data is to use x-y plots (those with two axes). Any geoscience data that show a relationship between two variables (distance vs. elevation, velocity vs. depth, etc.) can be plotted on an x-y graph. Some examples in introductory geosciences include topographic profiles showing what the land surface looks like, velocity of earthquake waves in the earth, the likelihood that a river will flood, the rate of glacial retreat.

## Why should I use x-y graphs?

Monthly Mauna Loa CO2 data (shown above) plotted on a x-y graph showing seasonal changes.
Bivariate (or x-y) graphs help us to visualize and categorize large volumes of data (like that at the right) without having to sort through cumbersome data tables. Imagine having to look at a table of 50-100 pairs of data and trying to figure out the relationship of one variable to another! It's much easier to see the relationship on a graph or plot! For example, looking at the table of data for atmospheric carbon dioxide collected on Mauna Loa, you might never recognize the important seasonal trends in the data that show up when 7 years of data (2000-2006) are plotted (to the left)!

## Graphing pages

These pages are designed to help you do complete exercises that are commonly associated with the use of graphs in the geosciences. In an introductory geoscience course, you might be asked to do one (or more) of three activities having to do with graphs. Decide which of these things you need help with and click on the link. (If you need help with all of these, begin with the first link and you will be directed to the next exercise from there.):

1. Plot points on a piece of graphing paper
2. Construct a line through the points you plotted (or that are already plotted). In introductory geosciences, there are two ways that you may be asked to do this.
• Construct a best fit line (a straight line that mimics the trend of the points)
• Connect points with a smooth curve
3. Read points off a line (either the one you constructed or one that is provided for you).