The Critical Zone. Illustration modified from original by Jemez-Catalina CZO.

The Critical Zone. Illustration modified from original by Jemez-Catalina CZO.

Read about:

Critical Zone Science

The Earth’s Critical Zone — from the tops of the trees to the bottom of the groundwater — is a constantly evolving boundary layer where rock, soil, water, air, and living organisms interact. Water and atmospheric gases move through the porous Critical Zone, and living systems thrive in its surface and subsurface environments, shaped over time by biota, geology, and climate. All this activity transforms rock and biomass into the central component of the Critical Zone — soil; it also creates one of the most heterogeneous and complex regions on Earth.

Measuring the total depth of a well and the water table depth.

Measuring the total depth of a well and the water table depth

Meeting the goals of Critical Zone science requires researchers with deep disciplinary knowledge as well as collaboration and integration across multiple disciplines.

Specialists are important because Critical Zone Science requires deep knowledge of many portions of the combined physical, chemical, and biological system. Close cooperation between specialists, each employing their own approach, helps to better understand interconnected Critical Zone processes. Concerted integration across disciplinary boundaries has been invaluable for solving questions that require a holistic approach.

The U.S. National CZO Program is tackling the fundamental questions of the Critical Zone with a systems approach. Find out more on the National Science Foundation (NSF) CZO page or visit criticalzone.org/national.

The REU/RET Program

National Science Foundation Research Experiences for Teachers (RET)  and Research Experience for Undergraduates (REU) programs aim to actively involve K-12 science educators and undergraduate students in meaningful, ongoing research projects.

REU/RET participants work closely on specific projects with faculty and researchers. Participants are granted stipends and, in many cases, assistance with housing and travel to the REU/RET site.

2016 CZO REU/RET Program Overview

Application Period: December 1, 2015 to February 15, 2016

Program duration: June 5-August 5, 2016

Capstone event: CUAHSI Biennial Colloquium on Science and Engineering in Shepherdstown, West Virginia, July 25-27, 2016

REU stipend: $500/week for up to 9 weeks. Local dormitory lodging will be provided for the entire program. Penn State REUs will receive a meal plan; Stroud Water Research Center REUs will receive a weekly food allowance. Reimbursement of travel expenses will be negotiated with prospective REUs.

RET stipend: $800/week for up to 9 weeks. Lodging and meals will be provided during the orientation. Penn State RETs will receive lodging and a meal plan for the duration of the program. Reimbursement of travel expenses will be negotiated with prospective RETs.


Stroud Water Research Center Research Engineer Steve Hicks deploying a sensor in a tributary of White Clay Creek.

Deploying a sensor in the CRB-CZO

Participants will begin with an intensive orientation program at the Susquehanna Shale Hills Observatory (SSHO) in the Appalachian Mountain Valley and Ridge physiographic province.

They will gain a broad understanding of the geology, hydrology, ecology, soils, and land use at the SSHO. Field activities may include a geophysical survey with ground penetrating radar, groundwater sampling, soil sampling, deploying field instrumentation, and performing surface water and plant studies.

Orientation will then move to the Christina River Basin Critical Zone Observatory (CRB-CZO) where participants will visit three experimental watersheds within the Piedmont physiographic province in southeastern Pennsylvania and northern Delaware, and compare and contrast it with that of the Appalachian Mountain Valley and Ridge physiographic province.

They will learn about the impacts of land-use change on the global carbon cycle, with a focus on how soil formation, erosion, and sediment transport can mobilize carbon.  They will also be introduced to data collection and management, building and deploying environmental sensors, and managing large data sets.

Field Research

Lysimeter sampling at Susquehanna Shale Hills CZO.

Lysimeter sampling at SSHO

REUs and RETs will be matched with a researcher, research topic, and specific site during the application and acceptance process.

When orientation is complete, all participants will have basic knowledge of the topics they and their colleagues will research as well as a broad understanding of Critical Zone science with which to frame their research investigations and results.

Each REU student will meet with a program manager to discuss the research topic they and their adviser have agreed upon.

During the remaining weeks of the program, participants will work on research topics with their faculty advisers, keeping records in individual online field notebooks and communicating with fellow participants in an online discussion forum.


All participants will be expected to create a poster or oral presentation for an end of summer REU/RET meeting at Shale Hills or Stroud. The final activity for the summer will be attendance at the CUAHSI Biennial Colloquium on Science and Engineering in Shepherdstown, West Virginia.

In addition to posters, RETs will be expected to develop curricular materials for public posting on the CZO REU/RET website.