For the Instructor

These student materials complement the Coastal Processes, Hazards and Society Instructor Materials. If you would like your students to have access to the student materials, we suggest you either point them at the Student Version which omits the framing pages with information designed for faculty (and this box). Or you can download these pages in several formats that you can include in your course website or local Learning Managment System. Learn more about using, modifying, and sharing InTeGrate teaching materials.

Activate Your Learning: High-Frequency Sea Level Change

What do you see in the data? What trends can you describe? You should be able to identify at least 3 observable trends or patterns present in these data. These form the basis for the questions below.

Question 1 - Essay

The first interval or trend that might be recognized lasts from ~5.5 to ~3.5 mya - What is the nature of this interval? How would you describe sea-level variation during this period?

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ANSWER:
Over this time period sea-level, although dynamic and with several scales of cycles, shows an overall average, long-term sea-level drawdown by a few meters to perhaps a almost 15 meters of sea-level fall (equal to about 10 to perhaps as much as 30 feet of long-term decline in sea-level). In shorter time scales, there are very short-term rise and fall events active on scales of a few thousand years, as well as cycles with durations of maybe a million years.

Question 2 - Essay

The second interval or trend that might be recognized lasts from ~3.5 to ~1 mya - What is the nature of this interval? How would you describe sea-level variation during this period?

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ANSWER:
Over this time period the rate of fall over the full duration became much more pronounced (steeper slope) indicating that sea-levels fell at a faster rate than during the preceeding time interval. Moreover the range over which sea-levels rise and fall becomes much more substantial and drastic. In the short-term, water levels may have oscillated by as much as 75 meters (~150 feet) within a just a few 1000 years. The million year cycles are still evident but are obscured by the extreme volatility in the high-order cycles that operate on the finer time scales. With regard to modern sea-levels, rarely within this time interval were sea-levels higher than they are today. Knowing that we are currently in a deglaciating interval today, it is highly likely that much of this long-term sea-level decline is coupled to growth of ice sheets on land.

Question 3 - Essay

The third interval or trend that might be recognized lasts from ~1 my to ~11,000 kya - What is the nature of this interval? How would you describe sea-level variation during this period?

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ANSWER:
For the last million years, data from this interval shows that sea-levels were primarily well-below the sea-levels of today. Extreme rates of rise and fall are noted with oscillations ranging up to 100 meters or more. The anatomy of these rise and fall events, when studied carefully shows lower rates of sea-level fall followed by more rapid sea-level rise events. This pattern will be explored in the coming section.

Question 4 - Essay

Over the last 5 million years (up to the beginning of the Holocene), how would you summarize the overall, integrated trend, into a cohesive statement about sea-level change?

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