Understanding weathering through museum-curated displays
Summary
The Natural History Museum's permanent exhibition, Restless Surface, offers an innovative setup for designing a laboratory activity for learners being introduced to Earth's surficial processes. Here, the potential of the topic of weathering being understood in an intrinsic way, based on the display of curated specimens is discussed. Reflections are made on the learner as well as the instructor's experience on visiting the gallery, and on pedagogical design for taking this way of learning further.
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Context
Audience
This activity is designed for an introductory course on Earth Science offered as a Natural Science elective. The students are non-majors in geoscience, taking this course to fulfill a general science requirement. They range from junior to senior years at Pepperdine University, studying at the London UK campus for an academic term.
Skills and concepts that students must have mastered
After a theoretical class lecture given by me the instructor, on the topic of weathering, students are given a short break, and then taken to the museum across the street, for the lab component of the course. An observation sheet (Table 1 (Microsoft Word 2007 (.docx) 12kB Mar20 21)), clipboard, and sheets of plain paper are distributed to each student before entering the museum.
How the activity is situated in the course
This activity is designed as one out of seven to eight laboratory or experiential learning activities for an introductory course on Earth Science.
Goals
Content/concepts goals for this activity
The subject of weathering as a surficial process is taught through this activity.
Higher order thinking skills goals for this activity
A number of concepts are pulled together all at once for the learner to understand and reflect upon:
The agents that enable weathering; the nature, availability and location of the material being weathered; the time involved, especially understanding it as an ongoing process; the outcome and its effect on the landscape; the application of weathered material in understanding paleoclimates, in agriculture, and geoengineering solutions for climate change.
Other skills goals for this activity
This activity is student-centered, involving independent as well as group work.
Description and Teaching Materials
INTRODUCTION
Teaching the topic of weathering for an undergraduate-level class lecture can be relatively straightforward to begin with. Students are introduced to three main processes of weathering such as mechanical, chemical and biological. Illustrated examples of the product of each type along with their pictures are also available on the World Wide Web. However, it is easier to find good pictorial examples of some types of weathering compared to other types. Pictures of the rock arches and canyons from the national parks of the western United States pose spectacular and convincing examples of mechanical weathering. Examples of rusting can be shown, and dissolution of salt and softer minerals can be spoken about and related to day-to-day examples. Despite it appearing to be a straightforward task, a number of concepts are pulled together all at once for the learner to understand and reflect upon.
Designing a laboratory activity on this topic within the typical class time of an hour and a half can prove to be challenging but it offers a scope for innovation at the same time. The permanent exhibition on Earth's surficial processes in the Red Zone of the Natural History Museum, called Restless Surface (Natural History Museum, n.d.), offers a way of teaching and learning the topic of weathering at a basic as well as a comprehensive level.
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BACKGROUND
Museums as resources for geoscience teaching
The role of geoscience exhibits in museums forming a popular part of excursions at various educational levels is well established. Museums in leading cities of the world, as well as regional and local museums take pride in their collections of fossils, rocks and minerals on display. Pop et al. (2004) have presented ways in which museum activities can be planned specifically for teaching about minerals. They argue for how museum displays allow for a formal, curriculum-based deductive learning, as well as the informal learning through inductive reasoning. Roscoe (1965) stated in his commentary on the geological education imparted to school children at the Chicago Natural History Museum, presently known as the Field Museum, that museum teaching techniques were effective as an addition to the curriculum, not as a replacement. He emphasized on the unique nature of museum resources providing primary sources for students to understand from, which may not be readily available within the educational curriculum. Here, a museum exhibit on surficial weathering of rocks is discussed, specifically its impact and use as a laboratory class, in adding to an undergraduate introductory geoscience curriculum.
MATERIALS AND IMPLEMENTATION
In this museum display called Restless Earth, starting with the main agents of weathering such as wind, water and ice, a combination of light and sound effects are used to convey their presence and role in the weathering and erosion process (Figure.1; MET Studio, n.d.). This effect helps in extending the viewer's imagination of understanding the process behind each display item, and can even generate further questions, as discussed below, in addition to the textual information provided with the displays and in the museum's bookstore (Janson-Smith et al., 2008).
The data gathering and sketching is done by the students while standing in groups before the displays in the gallery, mostly interacting with their cohorts, Guidance is given by me, the instructor, on how to collect data from the displayed specimens but the precise answers to be entered on the data sheet (Microsoft Word 2007 (.docx) 12kB Mar20 21) are left to the student to determine. Data and observations are gathered in three categories below:
Physical Weathering
The concept of physical or mechanical weathering of rocks by freeze and thaw, also known as frost wedging (Tarbuck & Lutgens, 2015), is presented through the product of this process, talus fragments, suspended by strings. This method of display can imply that they have come loose from the parent rock. A sound of shattering is played within this display case. It aids the viewer in imagining the process of rock fragments prising out from the parent rock, as the cracks and joints in the rock body widen due to continual freezing and melting of water within it. Reflecting on this process, it can remind the students of the physical principle of water expanding in volume on freezing, thus needing more space, exerting mechanical force within the cracks of the rock body to create it, and eventually widening it in the process and allowing the rock fragment to fall out. Further questions can be posed for students to reflect on:
Why are talus fragments typically seen in mountainous regions only?
Why are such accumulations not seen commonly near exposed rock formations on the plains?
How can mechanical weathering and its products be useful for paleoclimate analysis? Through it, the concept of frost shattering that would have occurred at the periphery of the ice sheets, i.e. periglacial weathering (Britannica.com, n.d.), from the last glaciation, and the rock debris that is still around, can be explored. Figure 2 represents talus fragments in nature (not from the museum display).
Chemical Weathering
One of the displays on chemical weathering shows two samples of Basalt rock, one before weathering and another after the process. One specimen is a chunk of black-coloured Basalt rock, and next to it is a small mound of powdery, cream-coloured clay, with no trace of the original rock. This stark contrast in the physical appearance of the end product of weathering from the parent rock is an image likely to be carried in the mind of the viewer. There are other samples of weathered rock in the museum, showing the altered state of the mineral feldspar in Granite, but these are more readily visible to the trained eye. A beginner may not be able to recognize at first glance, the difference in the sharpness of the crystal boundaries, in a large chunk of Granite rock, before and after weathering. Figure 3 (not from the museum display) represents weathered Basalt in nature, showing the stark contrast mentioned above.
Further reflection through a group discussion facilitated by the instructor, can bring out the applications of chemical weathering. One application is the use of Basalt rock dust as fertilizer (Gillman et al., 2002): through chemical weathering, the rock in its powdered state starts releasing mineral elements at a quicker rate due to more surface area available for the chemical reactions to take place (Tarbuck & Lutgens, 2015); the addition of these elements enriches the soil for agricultural use. A counter-reflection on this agro-engineering application as posing a possible hazard may also be discussed (Dalmora et al., 2016). A geoengineering application may also be discussed as follows: the artificially quickened chemical weathering process, by powdering the rock, in which the reaction involves the drawing down of carbon dioxide gas from the atmosphere, is being hailed as a solution for global warming (Lehmann & Possinger, 2020).
Biological Weathering
Biological weathering is displayed by a rock sample with imprints and remains of mollusk shells as well as holes in the rock, bored by the animal. This sample brings up an integrated concept of weathering, as it gets the viewer thinking about the biological action of the living mollusk. The image that can be conjured up in the mind of the student is that the living part of the mollusk is organic tissue which is soft compared to the rock, to say the least. The fact can then be raised and it is often thought of intuitively by the student, that the action involves the chemical secreted by the animal to bore a hole in the rock. Simultaneously, the example of bivalves boring into rock made of softer minerals, by the mechanical and abrasive action of their shells can also be brought up. Students have often asked the question as to whether such a sample of rock represents the combined processes of chemical, biological and physical weathering by the same agent, i.e. the bivalve.
Once the display specimen bearing rock borings by molluscs is understood by students as an example of biological weathering, the museum specimen display of a lichen-encrusted rock is understood more easily as another example of this type of weathering. At the same time, students have expressed their awe that lichen can be responsible for wearing away and removing rock material in the same way as a mollusk, by chemical secretion. An even more awe-striking concept of mineral-eating bacteria can then be brought up.
Sketching of curated specimens
A reaction often had from students in the first instance on entering the gallery is that they are not good at drawing objects and that their preference would be to take pictures. When it is mentioned to them that the assessment of the exercise is based on the effort made and the detail in the sketch such as the main features being annotated rather than the aesthetic appeal of the drawing, some take up the task with enthusiasm. A counter-argument is that capturing the specimen on a camera and annotating the picture inserted digitally on to their assignment is just as good and produces neater results. The importance of hand-drawing sketches while learning in nature science, with a focus on geology, has been discussed by Reichow (2018). His study highlights the enhanced performance of students on a geology course where sketching was an essential part of the curriculum. An essential factor pointed out in this study is that deep-level learning occurs when the student understands the key features that need to be sketched and annotated. His study also distinguishes between neatly labelled sketches, and conceptual sketches, with the latter often being the outcome of a process-based exercise such as studying weathering through artifacts. It has been observed that when given plain paper and a clipboard before the task, students are more likely to sketch and produce better quality work than when they are expected to use their own material. It is also mentioned to the students that the task of sketching while indoors is much easier and comfortable compared to sketching while in the open field, exposed to the elements of nature.
MATERIALS
- Table 1. Observation Sheet (Microsoft Word 2007 (.docx) 12kB Mar20 21)
Assessment
The assessment of this activity is done by grading 50% of the mark for a sketch with annotations and 50% for a brief description of the process as formulated in the data collection sheet (Table 1) given to the students. Students are expected to hand in their assignment right away after the completion of the lab activity. They have the option to go back to the classroom located across the street from the museum, if they wish to sit in class and complete the descriptive part of the assignment, and do additional research on their observations.
In the next class lecture after the activity, a follow-up discussion is held in class to give students the opportunity to talk about their museum-lab experience. During this session, there is an opportunity to take up the additional questions related to each type of weathering, mentioned earlier, in the section on Materials and Implementations. It allows for making connections between the process, outcome, and applications in science and society.
IMPLICATIONS
A direct implication of this lab activity and such others held in this course is that is triggers ideas for students to do their oral group presentation assignment. The item on the observation sheet asking to comment on the type of landscape or landform as an outcome of weathering, allows for linking the next class topic of erosion, transportation and deposition.
Another implication of this activity is for existing and future museums. Geoscience museums are typically known for their curation of fossils, minerals, rocks and gemstones. In this article, an uncommon curation of displays on the weathering process is presented along with its potential for pedagogy through experiential learning. There is a strong case to maintain and create museums and science learning centres, big and small, curated with specimens and images displayed in innovative ways to enhance teaching and learning and promote science literacy.
References and Resources
Britannica. (n.d.). Periglacial landform. https://www.britannica.com/science/periglacial-landform
Dalmora, A.C., Ramos, C.G., Oliviera, M.L.S., Teixeira, E.C., Kautzmann, R.M., Taffarel, S.R., De Brum, I.A.S., & Silva, L.F.O. 2016. Chemical characterization, nano-particle mineralogy and particle size distribution of basalt dust wastes. Science of The Total Environment 539, 560-565. https://doi.org/10.1016/j.scitotenv.2015.08.141
Gillman, G.P., Burkett, D.C., & Coventry, R.J. 2002. Amending highly weathered soils with finely ground basalt rock. Applied Geochemistry 17(8), 987-1001. https://doi.org/10.1016/S0883-2927(02)00078-1
Janson-Smith, D., Cressey, G. & Fleet, A. 2008. Earth's Restless Surface. Natural History Museum.
Lehmann, J., & Possinger, A. (2020). Removal of atmospheric CO2 by rock weathering holds promise for mitigating climate change. Nature 583, 204-205. https://doi.org/10.1038/d41586-020-01965-7
MET Studio. (n.d.). Restless Surface: Shaking up the Museums' permanent collection with a ground breaking, earth science-based experience. Retrieved December 2, 2020, from https://www.metstudiodesign.com/work/restless-surface
Natural History Museum. (n.d.). Restless Surface. https://www.nhm.ac.uk/visit/galleries-and-museum-map/restless-surface.html
Pop, D., Horák, J., & Hurlbut, J.F. (2004). Mineral Museums as Alliance Partners in Teaching Mineral Sciences. Journal of Geoscience Education 52(1), 87-96. https://doi.org/10.5408/1089-9995-52.1.87
Reichow, M. K. (2018). Does Sketching promote student learning? A review on undergraduate geology students. Journal of Learning and Teaching in Higher Education 1(2), 139-150. https://www108.lamp.le.ac.uk/ojs1/index.php/jlthe/article/view/826/2758
Roscoe, E.J. (1965). Elementary and Secondary Geological Education At the Chicago Natural History Museum, Journal of Geological Education, 13(1), 9-12. https://doi.org/10.5408/0022-1368-XIII.1.9
Tarbuck, E.J., & Lutgens, F.K. (2015). Earth Science. (14th ed.). Pearson.