These selections provides overviews of the early history of seismology and the start of geological oceanography. Both are geophysical studies that relied upon instrumentation to collect data. The key insights that come out of this work was the recognition of the Earth’s internal features, the differences between oceans and continents (based on marine geophysical data)

Harris, section 29

Allegre (1988) p. 24-34

This will give you a quick review of the development of seismology and the start of geological oceanography. (You will be reading more about the study of the oceans next time as we turn to the paleomagnetism.) This is a fairly straightforward account that is probably familiar to you. Allegre makes the interesting comment that the focus up to WWII was really on using seismology to determine the spherical geometry of the earth as a physics problem. The work on oceans initially dealt with the topology of the oceans but soon grew to include other featues.

Oldroyd (1996) Chapter 10: Thinking with Instruments: Earthquakes, Early Seismology and the Earth’s Hidden Interior

You will want to read p. 224-240 – this is a very concise history of seismology through about 1950 with a lot of information about instrumentation, conceptual frameworks, and the who/where of these developments. (You can skip the section from the bottom of p. 240 to p. 247 – it is a bit outside our interests.)

To do

The main interest today is seismology, so we need to “unpack” the information presented by Oldroyd. There are a few basic themes, each of which has its own story. In class, we will work to put these all in a common timeline.

• Development of instruments
  • What were the major advances in the development of instruments mentioned?
  • What were the centers for this work? Why there?
• Observations about the severity and distribution of earthquakes
  • What earthquakes had a long-lasting impact?
  • What kinds of maps and magnitude scales were initially constructed?
  • What was known about global distributions before the end of the 19th century?  How was this determined?
• Development of global networks of seismic stations
  • Who set them up?
  • When were they operational?
• Recognition of different types of seismic waves that travelled through the earth
  • List the types of waves and when they were recognized.
  • Who did this work? How was it related to the seismic observation systems?
• Development of a model for conditions inside the earth, primarily related to changes with depth (the familiar core, mantle, outer core, inner core, asthenosphere)
  • What was the sequence of discoveries about these internal features?
  • How were the recognized?
  • How did this model compare to the models used by geophysicists of the 1880s in their arguments about crustal thickness and stability?

Turning to marine geophysics, what was learned bout the oceans and the differences between oceans and continents?  What was the significance of:

• Topography of the sea floor
• Subsurface structure of the oceans (as revealed by seismic studies)
• Marine gravity readings

Links to course homepage and course schedule.