Unit 3.2 - Landforms and Remote Sensing
In this unit, geomorphic environments and the processes that can move and shape them are explored to learn about the links between landforms, soils, and the Critical Zone. The fundamentals of geomorphology are considered along with a somewhat detailed analysis of fluvial, eolian, glacial/periglacial, karst and coastal landforms and processes. Five book chapters are assigned as well as portions of fifteen web sites. The in-class activity focuses on remote sensing and aerial photographic analysis using resources available through the U.S. Geological Survey's EROS Data Center and other web sites. These resources should be considered as useful for developing the semester project, specifically for the purposes of identifying appropriate resources for a project as well as specifically for evaluating a study site, its landforms and landuse history, and the processes that may operate at the site.
The overall goal is to recognize that: 1) the lithosphere provides the solid framework onto which the CZ and ongoing processes within it develop and proceed; and, 2) diverse landscapes often contain similar landforms that may indicate similar processes of formation and similar physical, chemical and biological processes within it presently.
By the end of this lesson you should be able to:
- comprehend a soil catena and the influence of slope and aspect on pedogenesis.
- distinguish and assess some features and processes characteristic of five generalized geomorphic environments.
- apply knowledge gained to find remotely sensed imagery, specifically aerial photographs, for a study site cleared with your instructor.
Context for Use
This is the second of two units devoted to a study of the links between geology (here focused on geomorphology) and the Critical Zone. It was designed to meet the needs of an upper-division undergraduate or graduate-level seminar class meeting twice a week for 75 minutes. Each unit should take two class periods.
The preceding unit introduced the geomorphic concepts relating soil mantle thickness, the concept of a "feed through reactor", biota, and landscape position, to CZ architecture, and considered the variables associated with bedrock type, the rock cycle, tectonic setting, weathering and erosion -- this unit explores geomorphic environments and the processes that can move and shape them to learn about links between landforms, soils, and the CZ. As before, consider the outstanding question in Critical Zone science learned in a Lesson 1 reading (Brantley et al., p. 11): Can a unified approach be developed to characterize environmental conditions and mechanisms that produce different soil types, different CZ evolutionary pathways, and different CZ architectures?
Description and Teaching Materials
A remarkable aspect of Earth's surface is the seemingly infinite variety of landforms. However, some landforms possess certain characteristics that differentiate them from other landforms, a fact that is fundamental to geomorphology, the field-oriented study of landforms at the interface between geology and many other disciplines working to understand surface processes. The applications of geomorphic knowledge can range from engineering projects dealing with the physical properties of landforms to geological studies of the record of past climate change recorded by landforms. It is this overall lack of rigid philosophical boundaries that may be geomorphology's greatest attribute—interdisciplinarity (Ritter, D. et al., 2002, Process Geomorphology, 4th edition, p. 1–2).
Diversity in the Critical Zone is displayed by the distribution of soils across landforms, reflecting variable chemical and mechanical weathering processes as well as physical erosion and chemical denudation. These processes in turn control the internal structure of the Critical Zone, the feed-through reactor of Anderson et al. (2007), through which changes in surface area, flow paths, and material residence time impact element and nutrient weathering fluxes.
This unit begins with further consideration of the relationship between the CZ as a feed-through reactor and isostasy. Remember the Goodfellow et al (2016) and Heimsath et al (1997) papers and imagine a mountainous setting in which active erosion constantly removes weathered material from the summits: the unloading of weathered material allows the underlying crust to readjust by uplift, thereby physically raising unweathered rock rapidly into the feed-through reactor. Eventually the landscape may mature to one with low topography and little relief as the deep crustal root has been exposed, weathered, and brought toward isostatic equilibrium with the underlying mantle. Thick soil profiles develop and blanket underlying unweathered rock, slowing the rate at which the unweathered rock is processed through the reactor. Furthermore, recall from Lesson 2 that topography is the configuration of the land surface described in terms of elevation, slope, and landscape position differences, and that topography can hasten or retard the effects of climate on parent material-weathering by creating a balance between erosion and pedogenesis. Because topography often reflects the distribution of different parent materials in many landscapes, detailed soil maps can be useful for interpreting geology, and geological maps can in places be made directly from soil maps. Mappable soil bodies typically display patterns of distribution based on underlying bedrock and landforms—to fully understand the Crtical Zone and soils one must make an in-depth assessment of geomorphic settings.
The goal of this lesson is two-fold:
- to further introduce students to the geological processes that control the development, architecture and many processes in the CZ; and,
- to assess readily available remote sensing and aerial photography products to begin to learn to interpret landforms in the CZ.
Unit 3.2 - Day 1
For Unit 3.2 - Day 1, begin by assigning pre-class Reading Groups - Each group will pre-read and report on one of the 5 landscape categories outlined above ( fluvial, eolian, glacial/periglacial, karst and coastal). Have the students focus on general concepts that will help them to address goal 1 and more specifically the characteristic landforms and processes of each landscape category. The information contained in these web resources is meant to convey a very introductory level understanding of geomorphology and landform and process interpretation to those without a geosciences background. The information covered here will set the stage for an in-class discussion as well as for activities in the second day of class in this unit./p>
Pre-class Reading (individually)
- Read: Chapter 9 in Birkeland, P. W. (1999). Soils and Geomorphology (3rd ed.). New York: Oxford University Press.
- Make sure you understand the idea of a soil catena and (re)consider the effects of topography on the CZ -- think about how the feed-through reactor and chemical weathering fluxes might operate in a select study site and how they might vary between nearby environments.
Pre-class Reading groups selected from the 5 landscape categories outlined below: fluvial, eolian, glacial/periglacial, karst and shoreline processes and landforms. This information will set the stage for in-class presentations (10 minutes for each group) and a full class discussion of the Birkeland (1999) chapter and the landscape presentations.
Fluvial Landforms and Processes:
- This site provides a good general overview of fluvial landforms and processes, beginning with the hydrologic cycle and surface runoff. The site then provides a characterization of the parts and types of rivers, drainage patterns, fluvial processes of erosion, deposition, saltation, solution and suspension, and erosional and depositional landforms.
- This hyperlink overlaps somewhat with the one above. While studying this site, do not concern yourself with the details of specific drainage basins unless they are of interest to you. You can peruse the section on river types and drainage basin patterns for more detail than is available above. Do read the short sections on structure and tectonics, and paleochannels.
- Good images of stream channel types and features can be viewed by following this hyperlink:
Eolian processes and landforms:
- Study this reference to learn about eolian processes and landforms. Be sure to leave the site having grasped concepts covering the relationship between velocity, entrainment and transport, and the variety of erosional and depositional eolian landforms.
- For more detail and good imagery of dune fields check out the Pattern Indicators in:
- USACE (1991) Remote Sensing Field Guide - Desert(PDF, 363 pp; begin on p. 106 noting that some imagery is barely legible)
Glacial/periglacial processes and landforms:
- Use this site to review the causes of glaciation and glacier motion. Then review the anatomy of and types of glaciers, glacier erosion, sediment transport and deposition, and the resulting continental and alpine landforms.
- Ritter (2006) The Physical Environment, Ch.19, Glacial Systems
- Periglacial processes and landforms are described at the following web site focusing on permafrost, freeze-thaw weathering, ground ice, mass movement, and the erosive processes of gelifluction, wind and flowing water.
- For additional information, mostly review but with nice imagery, follow this hyperlink:
Karst processes and landforms
- Unique landforms and patterns of drainage called karst or karst topography primarily form in temperate to tropical regions, though they are found in arid and polar regions too. The common feature shared by all karst landscapes is that they are underlain by chemical sedimentary rocks particularly susceptible to dissolution, carbonates and/or evaporites. The landforms result mostly from chemical weathering of the host rock and the progressive integration of subsurface cavities, though collapse into solution cavities can also be important. Karst landscapes are often dominated by underground drainage networks that interrupt and capture surface water flow. For a relatively succinct definition of karst, from the Canadian perspective, follow this hyperlink:
- Of the karst-forming rocks, the carbonates (dolostone and limestone) are much more abundant than evaporites (mostly deposits of gypsum and anhydrite), therefore karst landscapes are most often found in regions underlain by carbonate rocks. The following Web site will help you learn more about limestone karst, including information on the relationship between lithology, porosity, permeability and karstification, the distribution of karstlands in the United States, the driving mechanics of karst processes, and links between surface water flow, aquifers and groundwater.
- Lemke (2013) UWSP, Karst Processes (link unavailable)
Shoreline processes and landforms:
- To learn about shoreline processes and coastal evolution, wave refraction and erosion, sediment transport and deposition, and submergent and emergent coastlines through a series of schematic diagrams, follow this hyperlink:
- A more basic review with colorful images of wave action, coastal processes, and images that help to identify coastal classification schemes can be viewed at:
- Ritter (2006) The Physical Environment, Ch.21, Coastal Landforms and Processes
- The following two hyperlinks lead to other reviews of coastal processes and landforms, as well as wave refraction, erosion, and deposition, importantly with nice images (from: Pidwirny (2006) Fundamentals of Physical Geography eBook)
- More information on classification, with nice imagery, can be studied at:
- GeoBytes: Coastal Erosion Features (blog, student made, slow videos)
- Review as a class (30 minutes)
- Class discussion of reading and presentations (25 minutes) focused on:
- Soil catena
- Role of topography
- Characteristic landforms
- Discuss the landforms/landscapes with respect to their associated climates and rock types and how that might influence CZ architecture. Consider questions like:
- Why are there limestone ridges in the Rocky Mountains when limestone underlies valleys in the Appalachian Mountains?
- Why are soils thick and deep in the tropics and shallow in glacial landscapes?
- Why are chemical fluxes higher out of basalts weathering in Hawaii than out of granitic terrains in Idaho?
Unit 3.2 - Day 2
Unit 3.2 - Day 2 introduces the concept that while field studies are essential for understanding the geomorphic environment or setting of a region, remote sensing imagery—specifically easily obtained aerial photographs and satellite imagery—provides a broad overhead view, a context in which to place field observations. In this section of the landform, you will first present an overview of the concepts of remote sensing and then individually or as group explore various online resources that provide overhead imagery. Before you begin the activity, instructors should browse the sites.
Activity - National Geo-PhotoFinder Activity
- Introduction to Remote Sensing and Aerial Photography (60 minutes)
- Consider using this tutorial: Earth Analysis Techniques: From the Outside Looking In — Changing Our Perspective of Earth
- NEON LIDAR video
- NASA - Earth from Orbit 2014 YouTube video
- MODIS Satellite
- SMAP Satellite
- SMAP at Work YouTube Video
- TRMM Satellite
- NASA Aqua Satellite
- Class demonstration (15 minutes)
- Activity Worksheet: GeoPhotoFinder activity (Microsoft Word 40kB Dec23 16)
Teaching Notes and Tips
The final phase of this class involves an in-class demonstration of a homework assignment. Use your own examples of landforms, perhaps from your area or region or a nearby state or national park, to demonstrate the approach the students should use when viewing the sites in the assignment. Be particularly vigilant to demonstrate how zooming in too close or not close enough can affect their assessment of the overall landscape and landforms.
Students will evaluate and interpret assigned aerial photographs to broadly classify the landscape/geomorphology of various regions in North America and compose a short report of their conclusions. The report will include a statement of aerial photographic resources available for their personal study site.
This assignment will be graded according to accurate recognition and interpretation of the aerial photographs using the "Short Essay Rubric" listed under course level assessment.
References and Resources
Links found in Day 2 Geo-PhotoFinder Activity