Geology Reference
In-Depth Information
EXERCISE
3
Measurements, Basic Calculations
and Conversions, and Graphs
INTRODUCTION
Scientific study of Earth requires careful observation,
description, measurement, and analysis of data that
are collected in the field and laboratory. Some of the
data are in numerical form and are obtained by mea-
surement of some quantity—such as the size of
pebbles on a beach, temperature of geothermal or
surface waters, thickness of a sequence of sedi-
ments, or location of stakes on a glacier. We then
study the patterns and trends in these data using
mathematics, tables, graphs, and maps to help us
understand the materials, processes, and landforms
of the Earth. With this approach we are able to estab-
lish the rates of processes, the nature of change in and
on the Earth and, if we really understand the system,
predict changes. The techniques used can be quite
sophisticated; however, there are basic calculations
that non-scientists can master that will help them
understand how the Earth system operates. Many of
these will be useful in day-to-day activities, also.
These are reviewed in this chapter; additional related
information is in Appendix I.
format for measurements, the results of science are
readily transformed from one nation to another and
from one discipline to another. The International Sys-
tem of Units, or SI Units, (Systeme International d'U-
nites), is similar to the metric (or CGS, centimeter-
gram-second) system. The standard base units most
often used in the geosciences are: meter (m) for dis-
tance, sec (s) for time, and kilogram (kg) for mass. Tem-
perature is measured in degrees Kelvin (K). But often
we use centimeters (cm), grams (g), and degrees Celsius
(C) because they are more convenient. So-called derived
units are formed through a combination of these base
units and sometimes other units, such as cm
2
, m
3
,
m
3
/sec (or m
3
s
_1
),and gm/cm
3
. Additional units are
given in Appendix I.
Unfortunately, the geosciences still use a combina-
tion of SI units (actually modified as metric units) and
English units to describe the size or dimensions of things
we measure in everyday activity. This situation makes it
easier for non-scientists to understand some things;
however, it means that in the geosciences we must often
deal with English units, for instance, on older topo-
graphic maps, contours and elevations are in feet. Other
than energy units (e.g., Btu), most of the measurements
employ modified SI units. Interfacing with old maps
and some disciplines that use English units requires that
we be able to switch from English to metric or SI units
(see the conversion tables in Appendix I). Actually, exer-
cises in this topic are in English or metric units. Eventu-
ally, the United States will make the transition to metric
to compete more effectively in international trade. One
additional advantage of SI is the ease of making conver-
sions from one set of units to another as shown below:
PART A. SCIENTIFIC MEASUREMENTS
AND NOTATION
In measuring a feature on the Earth, such as the width of
a stream, geoscientists obtain a quantity (a number) and
associated units (such as meters or feet). Standards have
been devised for measurements that ensure reliability
and uniformity in handling these numbers and units;
these standards include the International System (SI) and
other units, scientific notation, and significant figures.
1 kilometer (km) = 1,000 meters (m) = 1,000,000
millmeters (mm)
International System of Units
which is easier to work with than:
The International System of Units is the standard for
making scientific measurements. With a standarized
36
1 mile = 5,280 feet = 63,360 inches
