Studying Aquifers in Outcrop

Goals

• Visualizing ground water flow

Skills

• Observation, sketching and description of outcrop features
• Correlating stratigraphic, post-depositional and structural features with groundwater flow
• Explaining a scientific phenomenon (groundwater flow) in layperson's terms
• Estimating rates of groundwater movement

This lab can be used to augment or replace more traditional outcrop descriptions. In a physical geology course, it might become a field lab on local stratigraphy. In an environmental geology course, it might substitute for a local stratigraphy lab.

I use this lab in tandem with a pump test exercise. Each works perfectly well on its own, too.

This lab can take between two and four hours.

Equipment needs:

• Meter sticks or staffs marked in decimeters or tape measures
• compasses
• bottles of water (optional)

Depending on how detailed you want the students' descriptions of the outcrop features to be, this lab can take anywhere from two hours to more than four hours. Three hours (about an hour at each of two exposures with travel time in between) is enough time for students to describe the rock features, do some sketching, ask questions, take notes and understand the major hydrogeological implications of the outcrops. It is not enough time to construct detailed stratigraphic sections of more than a meter, particularly in a rock unit as complex as the Jordan Formation (a major aquifer in parts of Minnesota and Wisconsin). As an instructor, you will have to decide on your priorities and convey them to the students.

Because the concept of "aquifer" is a difficult one for both students and the general public, an interesting assignment based on this field lab is to have students write a commentary piece for the campus or town newspaper, describing how water moves through the ground, what an aquifer is, and why people should care about aquifers.

Students' sketches, detailed stratigraphic sections and writing based on this field lab can be assessed for understanding, clarity of diagrams and writing, and accuracy (both of concepts and of the specifics of the units). This lab also forms a good basis for written essay quiz and exam questions.