FIGURE 1.10 Paleontologists study ancient life. Here scientists are excavating the remains of Albertasaurus, a large
carnivore similar to Tyrannosaurus rex, which lived during the late Cretaceous Period. The excavation site is near Red
Deer River, Alberta, Canada. The aim of historical geology is to understand the development of Earth and its life
through time. Fossils are essential tools in that quest. (Photo by Richard T. Nowitz/Science Source/Photo Researchers, Inc.)
CHAPTER 1 An Introduction to Geology
10
Do Glaciers Move?
An Application
of the Scientific Method
In Figure 1.9 you learned that specialized
instruments aboard satellites allow us to
monitor glaciers from space. This, of
course, is a recent breakthrough. In the
19
th century learning about the behavior of
glaciers was far more difficult and laborious. The study of glaciers provides an early
application of the scientific method. High
in the Alps of Switzerland and France,
small glaciers exist in the upper portions of
some valleys. In the late 18
th and early 19
th
centuries, people who farmed and herded
animals in these valleys suggested that
glaciers in the upper reaches of the valleys
had previously been much larger and had
occupied downvalley areas. They based
their explanation on the fact that the valley
floors were littered with angular boulders
and other rock debris that seemed identical
to the materials that they could see in and
near the glaciers at the heads of the valleys.
Although the explanation of these
observations seemed logical, others did
not accept the notion that masses of ice
hundreds of meters thick were capable of
movement. The disagreement was settled
after a simple experiment was designed
and carried out to test the hypothesis that
glacial ice can move.
Markers were placed in a straight line
completely across an alpine glacier. The
position of the line was marked on the
valley walls so that if the ice moved, the
change in position could be detected. After
a year or two the results were clear. The
markers on the glacier had advanced down
the valley, proving that glacial ice indeed
moves. In addition, the experiment demonstrated that ice within a glacier does not
move at a uniform rate, because the markers in the center advanced farther than did
those along the margins. Although most
glaciers move too slowly for direct visual
detection, the experiment succeeded in
demonstrating that movement nevertheless
occurs. In the years that followed, this
experiment was repeated many times with
greater accuracy using more modern
surveying techniques. Each time, the basic
relationships established by earlier attempts
were verified.
The experiment illustrated in
FIGURE 1.11 was carried out at Switzerland’ s
Rhône Glacier later in the 19
th century. It
not only traced the movement of markers
within the ice but also mapped the position
of the glacier’ s terminus. Notice that even
though the ice within the glacier was
advancing, the ice front was retreating. As
often occurs in science, experiments and
observations designed to test one hypothesis yield new information that requires
further analysis and explanation.
C O N C E P T C H E C K 1 . 5
How is a scientific hypothesis different
from a scientific theory?
List the basic steps in many scientific
investigations.
2
1
carnivore similar to Tyrannosaurus rex, which lived during the late Cretaceous Period. The excavation site is near Red
Deer River, Alberta, Canada. The aim of historical geology is to understand the development of Earth and its life
through time. Fossils are essential tools in that quest. (Photo by Richard T. Nowitz/Science Source/Photo Researchers, Inc.)
CHAPTER 1 An Introduction to Geology
10
Do Glaciers Move?
An Application
of the Scientific Method
In Figure 1.9 you learned that specialized
instruments aboard satellites allow us to
monitor glaciers from space. This, of
course, is a recent breakthrough. In the
19
th century learning about the behavior of
glaciers was far more difficult and laborious. The study of glaciers provides an early
application of the scientific method. High
in the Alps of Switzerland and France,
small glaciers exist in the upper portions of
some valleys. In the late 18
th and early 19
th
centuries, people who farmed and herded
animals in these valleys suggested that
glaciers in the upper reaches of the valleys
had previously been much larger and had
occupied downvalley areas. They based
their explanation on the fact that the valley
floors were littered with angular boulders
and other rock debris that seemed identical
to the materials that they could see in and
near the glaciers at the heads of the valleys.
Although the explanation of these
observations seemed logical, others did
not accept the notion that masses of ice
hundreds of meters thick were capable of
movement. The disagreement was settled
after a simple experiment was designed
and carried out to test the hypothesis that
glacial ice can move.
Markers were placed in a straight line
completely across an alpine glacier. The
position of the line was marked on the
valley walls so that if the ice moved, the
change in position could be detected. After
a year or two the results were clear. The
markers on the glacier had advanced down
the valley, proving that glacial ice indeed
moves. In addition, the experiment demonstrated that ice within a glacier does not
move at a uniform rate, because the markers in the center advanced farther than did
those along the margins. Although most
glaciers move too slowly for direct visual
detection, the experiment succeeded in
demonstrating that movement nevertheless
occurs. In the years that followed, this
experiment was repeated many times with
greater accuracy using more modern
surveying techniques. Each time, the basic
relationships established by earlier attempts
were verified.
The experiment illustrated in
FIGURE 1.11 was carried out at Switzerland’ s
Rhône Glacier later in the 19
th century. It
not only traced the movement of markers
within the ice but also mapped the position
of the glacier’ s terminus. Notice that even
though the ice within the glacier was
advancing, the ice front was retreating. As
often occurs in science, experiments and
observations designed to test one hypothesis yield new information that requires
further analysis and explanation.
C O N C E P T C H E C K 1 . 5
How is a scientific hypothesis different
from a scientific theory?
List the basic steps in many scientific
investigations.
2
1