The Natural Science of the Caribbean

Introduction

The first half of “The Natural Science of the Caribbean” examines hurricanes, earthquakes, volcanoes, and tsunamis from a physical science perspective, discussing the underlying processes governing their generation and the various factors that influence such things as the strength/magnitude of each event.  But before these topics can be discussed in any detail some basic knowledge about the workings of the natural world must be presented.  For example, prior to examining the process of hurricane formation we first examine global weather and wind patterns, atmospheric structure, and ocean currents and sea surface temperatures.  Similarly, presentation of earthquakes and volcanoes warrants an introduction of basic geology, while comprehension of tsunami motion requires previous discussion about wave properties and propagation.  Emphasis is placed on the unifying concept that each of these events result in a movement or release of energy.  The second half of the course examines these phenomena from a biological perspective, discussing the impact(s) of each on our islands’ terrestrial and marine ecosystems. 

The focus of this paper is to present selected examples that highlight the integration of various chemical principles with specific course topics under discussion.  Brief mention of biological topics are included in order to provide a more complete overview of the entire course content, as this aspect of the course is subject for another discussion.  For more information, please feel free to contact the author.

Course Logistics

This course meets for two 50-minute lectures and one 3-hour laboratory per week offered at two different lecture times (day and evening) and four or five laboratory times (weekday and weekend).  Class size is typically 80 students each semester split between the two lecture sections.  The lecturers are full-time faculty and both attend all classes presenting in turn, while the other is present to add to the discussion by asking questions or offering further information.  The labs are taught by a combination of full- and part-time faculty.  Peer mentors are an integral part of this course.  Students who have previously taken the class, performed strongly, and have demonstrated enthusiasm are invited to become peer mentors.  They function as role models and provide an additional resource for student questions, as well as to assist the instructors during the lab with logistics and student support.  We usually have 2-3 peer mentors each semester, and they attend all lectures and the lab section(s) to which they have been assigned.
            
Full-time faculty receive 2 credits each for teaching half of the lectures, plus 0.66 credit each for weekly collaborative meetings during which we discuss how the previous weeks’ lecture and labs went and how they can be improved for the next semester.

Course Content

We begin by providing an overview of how the content of the course is to unfold over the semester.  Hurricanes, earthquakes, volcanoes, and tsunamis receive a general introduction and we present the idea that all of these events have something in common – the release of stored energy.  The four phenomena are compared and contrasted in terms of their duration and period of worry.  Introduction of basic definitions such as mass, weight, and volume are presented early and the concept of expansion of a gas upon heating and contraction upon cooling (Charles’ Law) is linked to the newly-defined concept of density.  This establishes a foundation upon which discussion of energy transport via convection will be developed later in connection with hurricane structure and function, global wind and weather patterns, and plate tectonics.
            
The Scientific Method, the Metric System, and Unit Conversion.  We next introduce the approach used by scientists when problem solving.  We recognize different ways of seeking knowledge from philosophy to religion to art and stress that, while each of these approaches are valid, we will be focusing on learning about our environment from a scientific perspective.  The individual steps of the scientific method are presented, and we talk about the formation, testing, and potential revising of hypotheses based on repeated scientific measurements and observations and point out that this is a continuing process.  Exercises to develop critical-thinking skills are performed by presenting simple experiments and their results and asking the students to identify statements that are observations, interpretations, and assumptions, and finally, to draw conclusions based on the data.  The difference between a fundamental and a derived property is presented in conjunction with the metric system and unit conversion.   A portion of one of the labs is devoted to working with the metric system and performing conversion exercises.
            
Maps.  A basic survey of map reading and location identification using latitude & longitude and distance and relative direction is presented – again, as a foundation builder for when we track the path of a hurricane or the location of the epicenter of an earthquake or plate tectonic boundaries.
            
Weather.  A discussion of weather provides the foundation for understanding our first natural phenomenon – hurricanes.  We start by distinguishing between weather and climate and introduce basic weather instrumentation that is used to measure and describe the condition of the atmosphere (i.e. thermometer, barometer, anemometer, and psychometer).  Presentation of atmospheric layers and their characteristics provide an opportunity to point out how gas density and temperature change as a function of altitude, with specific emphasis on the troposphere where weather occurs.  The sun is revealed as the source of all weather, warming the Earth’s surface.  This energy is then re-radiated provides the basis of convection – warming from the bottom.  The Coriolis force and zonal wind systems are the result of the Earth’s rotation.  Converging Hadley cells produce regions of low pressure at the surface of the earth where the cells meet and are associated with “bad” weather, while diverging Hadley and Ferrel cells are associated with “good” weather as regions of high pressure exist at their junction.  The tilt of the earth is responsible for the movement of the inter-tropical convergence zone (ITCZ) north during the summer (resulting in our hurricane season) and south during the winter.
            
Hurricanes.  We now have enough background information to move on to the lively topic of hurricanes.  We speak about the life cycle of a hurricane (a.k.a. cyclone, typhoon); its birthplace and anatomy and conditions required for its formation and ultimate destruction.  We begin general and move towards specifics.  A world map is displayed illustrating the typical areas where hurricanes form, their common paths, and annual percentages and we ask the students to tell us what they observe.  Students note that hurricanes seem to originate just north and south of the equator, but not at the equator and that the waters in which they are forming over are warm.   Other formation requirements which we add to the list are warm, humid air with a cold air mass and weak upper-level horizontal winds above.  We leave these observations for them to ponder as we continue our introduction.  
            
The progression of storm classification (tropical disturbance or wave to tropical depression to tropical storm to hurricane), their respective characteristics (i.e. wind speed range, extent of organization, anatomy), and their weather symbols are explained.  Next we discuss several factors that affect the path of a hurricane.  Strong steering winds such as the trade winds and the westerlies make for more easily predicted paths than weaker steering winds.  High-pressure weather systems act as a barrier or wall through which hurricanes cannot pass without significant disruption of structural organization.  The presence of such a system, like the Bermuda High, can prevent the northward curving of the storm as directed by the Coriolis force, causing it to potentially make landfall along the eastern or southern seaboard of the US, Central America, and/or other western Caribbean islands like Cuba and Jamaica.  Lastly, the hurricane’s place and time of origin can determine its path.  If, for example, the storm begins to form in the colder Atlantic waters of the north, it will not have sufficient energy to strengthen.  Movement of the inter-tropical convergence zone also contributes to path direction.  Storms forming early in the hurricane season (July – Sept) typically track from the east and curve north and west.  However, later in the season (Oct-Nov), as the ITCZ has shifted south, more hurricanes approach us from the west and move to the northeast.
            
Now on to the actual mechanism of hurricane formation and strengthening.  We revisit the notion that hurricanes do not form at the equator due to a lack of Coriolis force required for sufficient rotational development.  So, if a tropical depression is far enough from the equator it can develop a center of rotation and low pressure.  If the low pressure center of the storm is over warm water, some of the water will evaporate increasing the amount of water vapor in the air.  As this warm, humid air rises the temperature of the atmosphere is decreasing, thus the water vapor condenses and forms clouds.  The process of condensation releases energy (a.k.a. latent heat) into the surrounding air which then warms, expands, and rises even higher.  This rapid movement of air further decreases the pressure immediately below it, which in turn causes even more warm, moist air at sea level to evaporate at a faster rate.  With this increase in evaporation comes an increase in condensation, which causes more latent heat to be released, which causes more water vapor to evaporate at sea level, and on and on.  The continued decrease of air pressure at sea level also causes surface wind to blow faster and faster toward the center of low pressure, creating turbulent waves that produce sea spray that lend to a further increase in the rate of evaporation.  A giant spinning convection cell is created that has the ability to feed and strengthen itself – a self-sustaining positive feedback system.  Much time is spent ensuring that the students comprehend the sequence of events and, especially, the chemical principles that govern them.
            
The next question, naturally, is how such powerful systems weaken and die.  We solicit answers from our students, hinting that they should consider what the storm needs to “live” and that if those things could be taken away the strength of the storm would decrease.  Removal of moisture by movement over a large land mass and/or removal of warm water by either movement north into cooler waters or by crossing/following the path of a previous storm that has depleted the heat energy in the water are possible causes of weakening or death.  Strong upper level wind can also shear or inhibit organization of a proper convection cell.
            
We conclude our discussion of hurricanes addressing the potential damage that can result from high winds and storm surge depending on its strength according to the Safir-Simpson scale and other factors such as topography.
            
Geology.  Our focus now shifts towards basic geology so that we can investigate earthquakes and volcanoes.  The presentation of minerals as the building blocks of rocks, their composition, and physical properties such as hardness and cleavage lead into discussion of the Earth’s layers and the chemical composition of the Earth’s crust.  From there we distinguish between igneous, sedimentary, and metamorphic rock classification and formation and present the rock cycle. 
            
Igneous rocks form when molten rock cools and solidifies, and the location of this event determines whether it is deemed intrusive or extrusive.  We explain that molten rock that cools slowly within the earth (intrusive) has more time to organize itself into relatively large, granular crystals while small to no crystals result from ejected molten rock which cools much more rapidly leaving little to no time for significant organization (extrusive).  St. Croix has two small areas of exposed igneous rock,, and pumice from Montserrat (and other volcanic islands) often washes up on our south shores.  
            
Sedimentary rocks are further subdivided into clastic, chemical, and organic referring to their origin.  Our island is unique in that, while most other islands of the Caribbean are volcanogenic, St. Croix is primarily a sedimentary island.  We have clastic sedimentary rock in our western mountains from the deposition and subsequent compaction of volcanic ash from active volcanoes in the region.  The middle of our island is composed of chemical sedimentary rock, namely precipitated calcium carbonate (limestone).  In lab, students test for the presence of calcium carbonate in various rock samples taken from around the island by observing its reaction with hydrochloric acid.  They simply place a drop or two of 1M HCl on the sample and watch for the evolution of carbon dioxide as evidenced by the formation of tiny bubbles.  
            
Tremendous temperature and pressure within the earth result in the formation of metamorphic rock.  We note that elongated minerals tend to orient themselves parallel to each other and perpendicular to the direction of pressure in an effort to minimize stress.  This process of foliation can be seen in some rocks.  A minute amount of metamorphic rock can be found at the easternmost end of St. Croix.  While on our field trips around our island, we point out examples of each type of rock discussed in lecture and examine/comment on the presence of organic material contained within the exposed layers.
            
Alfred Wegener’s continental drift theory and Harry Hess’s proposal of sea-floor spreading based on ocean floor anomalies set the stage for plate tectonic theory.  The types of plate boundaries are examined with respect to plate density resulting in the subduction of the more dense plate beneath the less dense plate.  The driving force behind the motion of the plates is convection within the Earth’s mantle.  It is this motion that is responsible for mountain-building, the destruction and formation of the Earth’s crust, earthquakes, and volcanoes.
            
Earthquakes.  The motion of the plate sections is not a smooth, well-lubricated movement; in fact, when plates move there is a sudden and very powerful release of stored energy accompanied by the generation of seismic waves.  Wave properties (wavelength, amplitude, period, and frequency) are defined as well as the distinction between the different types of seismic waves (S-, P-, and L-waves), their characteristics and differing abilities to penetrate layers within the earth based on its composition.  In lab, students use the difference in arrival times of the S and P waves at three different detecting stations to locate the epicenter of an earthquake.  The magnitude and location of the most recent earthquakes in our region are mapped and correlation between earthquake and plate boundary locations is noted.
            
Volcanoes.  The release of energy from a volcano is most obvious to students.  The characteristics of a lava-dominated eruption vs. an explosive eruption are compared and contrasted.  A lava-dominated eruption contains minerals rich in magnesium and iron.  This darker-colored mafic lava is of fairly low viscosity and thus produces lava fountains, lakes, and rivers that flow long distances and tend to produce relatively flat or slightly mounded volcanoes, like in Hawaii.  In contrast, the lava of explosive eruptions is typically rich in silicate minerals and poor in magnesium and iron.  This type of very sticky, highly viscous felsic lava tends to form volcanoes of a steeper slope.  The different types of volcanoes presented include shield, cinder cone, submarine, and stratovolcanoes.  Location of volcanoes along convergent plate boundaries is mapped, and students are reminded of the connection of earthquake location previously addressed.  We then discuss the location, formation, and eruption history of several volcanoes found here in the Caribbean – Mt. Pelee in Martinique, Soufriere Hill in Montserrat, and Kick ‘em Jenny off the northern coast of Grenada.
            
Ocean and Wave Motion.  Ocean movement is absolutely essential as it affects weather, reduces differences in salinity and temperature between ocean areas, helps dissolve oxygen, brings food to many marine organisms, and disperses their waste products, as well as swimming and floating organisms.  The mechanism by which the ocean circulates is quite complex and only the main ideas are addressed.  Water temperature and salinity together determine the density of seawater and differences in density between large water masses results in the vertical mixing of the ocean.  This thermohaline circulation largely determines the climate of the Earth and, through the process of upwelling, brings vital nutrients closer to the oceans’ surface to be utilized by phytoplankton that form the basis of the aquatic food web.
            
Surface wave action diminishes rapidly with depth and serves to transfer energy across vast distances, but it is only the wave energy, not the individual water molecules, that moves across the sea surface.  Waves are generated by the wind and are influenced by wind velocity, duration, and fetch.  As a wave approaches the shoreline it is slowed by friction with the ground beneath it, slowing the base of the wave more than the top.  The wave gets higher and steeper until ultimately the top of the wave topples over creating surf.
            
Tsunamis.  Many events can generate a tsunami given sufficient magnitude.  For example, underwater earthquakes, large landslides into an ocean body, eruption of a submarine volcano, meteor impact – in fact, any disturbance that suddenly displaces a large volume of water.  Tsunamis are characterized as having very long wavelengths and short amplitudes when in deep water.  However, these characteristics change significantly just as any other wave as it approaches land – the wavelength shortens and the amplitude heightens – only on a much larger scale and with potentially devastating impacts.  We recall the tsunami of 1867 that resulted from a magnitude 7.5 earthquake centered north of St. Croix.  Two tsunami, approximately 7.6 m in height, were generated by two separate shocks.  Both crashed on the shores of Frederiksted, St. Croix and left one large US Naval ship beached and five people dead.  Tsunami detection and monitoring systems are discussed.         
            
Biological Content.  The balance of the course focuses on these topics from a biological perspective and content is listed to only to provide a general overview.  Lectures topics include: an introduction to ecology; biodiversity; mangrove ecosystems; seagrass beds; coral reef ecosystems; the affect of natural and anthropogenic disturbances on ecosystems and biodiversity.

Course Structure

Quizzes.  Weekly quizzes are given at the beginning of each laboratory period.  This 10-minute quiz covers material from the lectures that week, as well as one or two questions about the lab that will be performed that day.  Administering quizzes during lab allows for more lecture time and provides incentive for the students to read that weeks’ exercise/activity before coming to lab.  Quiz format typically includes multiple-choice, fill-in-the-blank, and short answer written by all instructors.

Exams.  There are three exams spaced evenly throughout the semester worth 100 points each.  They are administered in the lecture setting to allow all students to take the exam at the same time.  Exam format typically includes multiple-choice and fill-in-the-blank questions written by all instructors.  The two-hour final exam is cumulative and is of the same format as regular exams.

Laboratory.  The activities and exercises selected for lab are chosen to complement and reinforce the current lecture material in addition to building skills to make them stronger, more successful students.  These include: basic computer skills, plagiarism exercise, how to take scientific measurements, map reading, building simple weather instruments, hurricane tracking, classification and chemical composition of rocks, epicenter mapping, and three field trips – which are always the most popular labs.

The field trips are scheduled towards the end of the semester when the bulk of the course has been presented.  This allows us to incorporate all that we’ve learned in the course and apply it to the “real world.”  We begin with terrestrial ecosystems, and then move toward the water to investigate coastal and marine ecosystems.  
            
The first field trip involves a walk/hike in our tropical moist forest.  We are accompanied by an entomologist who identifies our local tree and insect species, discusses interactions between different species of organisms specific to that area, and asks and answers questions about this particular ecosystem.  We also point out examples of sedimentary rock composed of volcanic ash along the way.  Their lab exercise is to measure the abundance of plant species within an assigned transect and to analyze and explain the distribution of their data via a lab report.  
            
Our second adventure outdoors investigates a mangrove ecosystem where students learn to identify and describe red, black, and white mangroves as well as understand the differences among the three.  Each has adapted a unique way of tolerating such a high-salt environment.   Sea grass beds and coastal vegetation are also discussed.  
            
Our last field trip brings us to the shallow waters of a nearby beach to examine a marine ecosystem.  This beach, rich in various aquatic organisms, also offers closer examination of vast sea grass beds, algae, and local rock formations different from that found in the forest.

Directed Information Retrieval (DIRs).  Four DIRs are assigned over the semester.  Students are to search the popular media (i.e. newspapers, magazines, and internet) for current articles relevant to our course.  They are to read and summarize (~150 words) the article and state how the article relates to SCI 100.  This is an effort to connect current events with science and course content and to illustrate that science is not just something that is done in a laboratory, but that it is everywhere in the world around us, everyday.

Science Conference Paper and Presentation.  In an effort to mimic the experience of writing and presenting research at scientific conferences, students are required to write a short (~3-5 pages) paper on an approved topic of their choice that is related to the subject matter in our course.  They are shown how to search specific scientific journals for relevant articles, explained what each section of a research paper contains, and given guidelines on how to present their paper to their peers in lab at the end of the semester.

Extra Credit.  Students are given two opportunities to earn extra credit.  The first is the construction of a portfolio of all of their work for the semester.  Students are then asked to analyze this collection of work and write a 1-2 page evaluation of the quality of said work and how it changed throughout the semester.  Comments concerning the operation and presentation of the course are solicited, specifically asking the students to indicate what aspects of the course they particularly enjoyed and any recommendations they might have on improving the course.  The portfolio is submitted on the day of the final exam.  
            
The second extra credit opportunity involves participation in Campus Wide Experiences (CWEs) that occur throughout the semester.  These activities are held outside of normal class times and have included guest speakers and seminars on pertinent topics; tours of UVI’s aquaculture, model farm, and animal research facilities, our local botanical gardens, UVI’s wetland reserve; beach clean-ups; movie nights featuring films related to course content; attendance at UVI’s Spring Research Symposium, etc.  Students are encouraged to attend as many CWEs as they wish, but a maximum of two activities are counted as extra credit.  Again, this is an attempt to connect course material to the “real world”. 

Evaluation of Students.  All coursework is graded by the lecturers and/or lab instructors.  Grades are assigned using the standard grading scale with traditional letter grades.  Each component is weighted as follows:

Closing Remarks

This course provides students with a glimpse of their island home through the eyes of a biologist, a chemist, a physicist, a meteorologist, and a geologist – that’s a lot of eyes!  We hope that our attempt to present the natural world using a variety of fields will spark interest and inspire some of them to take a closer look.

Acknowledgements

Special thanks to Drs. Michelle Peterson, Stuart Ketcham, and Adam Parr for their continual support and encouragement and to Dr. Roy Watlington for providing a wealth of information about the design of the course.

CONFCHEM on-line conferences are organized by the ACS Division of Chemical Education's Committee on Computers in Chemical Education ( CCCE ). Send additions or corrections for this page to John H. Penn at John.Penn@mail.wvu.edu .