Laboratory Study of Stick-Slip Behavior and Deformation Mechanics of Subglacial Till

Summary

This data set includes the results of laboratory experiments examining the constitutive properties of subglacial till, under dynamic stressing. The data include the results of shear strain and stress experiments. Testing was carried out in a servo-controlled biaxial shear device under controlled temperature and stress conditions, allowing both sliding and microstructural processes to be studied in detail. Till samples were collected from Matanuska, Alaska, and from Caesar till at the Laurentide Ice Sheet.

The data are available via FTP in ASCII text format (.txt). Figures are available as Encapsulated Postscript (.eps) files.

Citing These Data

We kindly request that you cite the use of this data set in a publication using the following citation example. For more information, see our Use and Copyright Web page.

The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, publisher: NSIDC, and digital media.

Anandakrishnan, S., and C. Marone. 2010. Laboratory Study of Stick-Slip Behavior and Deformation Mechanics of Subglacial Till. Boulder, Colorado, USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5WH2MX7.

Overview Table

Category Description
Data format Data are in ASCII text (.txt) format.
Spatial coverage and resolution Experiments were conducted in a laboratory setting, with till samples collected from the following locations.

Matanuska Glacier Till Sample 2:
Southernmost Latitude: 61°46.907' N
Northernmost Latitude: 61°46.907' N
Westernmost Longitude: 147°45.178' W
Easternmost Longitude: 147°45.178' W

Matanuska Glacier Till Sample 4:
Southernmost Latitude: 61°46.766' N
Northernmost Latitude: 61°46.766' N
Westernmost Longitude: 147°45.537' W
Easternmost Longitude: 147°45.537' W

Caesar Till:
Southernmost Latitude: 40°4'2" N
Northernmost Latitude: 40°4'2" N
Westernmost Longitude: 83°00'25" W
Easternmost Longitude: 83°00'25" W

Temporal coverage and resolution Laboratory experiments were performed from 2004 to 2007.
File naming convention p1025.txt
p603.txt
File size Files range in size from 250 KB to 3438 KB.
Parameter(s) Shear Stress
Shear Strain
Shear Strength
Layer Thickness
Time
Procedures for obtaining data Data are available via FTP.

Table of Contents

  1. Contacts and Acknowledgments
  2. Detailed Data Description
  3. Data Access and Tools
  4. Data Acquisition and Processing
  5. References and Related Publications
  6. Document Information

1. Contacts and Acknowledgments

Investigator(s)

Dr. Sridar Anandakrishnan
Department of Geosciences
442 Deike Building
Pennsylvania State University
University Park, PA 16802
USA

Dr. Chris Marone
Department of Geosciences
536 Deike Building
Pennsylvania State University
University Park, PA 16802
USA

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgements

This research was supported by NSF OPP grant 0440523.

2. Detailed Data Description

Format

Data are in ASCII text format (.txt). Figures are available in Encapsulated Postscript (.eps) format.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/marone_nsidc_0460/ directory. Within this directory, there is a Microsoft word document, ExperimentTable.doc, that lists the conditions for each experiment in the data set.

Table 1. Directory Description
Directory Description
Creep_Experiments Constant shear stress experiments
Friction_Experiments Constant shear velocity experiments
Figure_Data Data files used to produce the figures in Rathbun, et. al.
Figure_Images Figure image files from Rathbun, et. al., in Encapsulated Postscript (.eps) format.

File Naming Convention

Files are named according to the following convention and as described in Table 2:

pXXXsYtrZ.bin

Where:

Table 2. File Naming Convention
Variable Description
pXXX Experiment number, where XXX indicates a number between 491 and 1261 (Experiment numbersin this data set are not sequential.)
s Contact area size:
Lowercase "s" indicates a 5cm x 5cm contact area.
Uppercase "S" indicates a 10cm x 10cm contact area.
Y Initial layer thickness, in mm
t Till
r Rough boundaries
z Normal stress in MPa
.bin File extension

Example: p490s10tr.5.txt contains data from experiment number p490, with 5 cm x 5 cm contact area, 10 mm layer thickness, till with roughened edges, at 0.5 MPa normal stress.

File Size

Files range in size from 250 KB to 3438 KB.

Spatial Coverage

These data were collected during laboratory experiments, using till collected from three sites:

Matanuska Glacier Till Sample 2:
Southernmost Latitude: 61°46.907' N
Northernmost Latitude: 61°46.907' N
Westernmost Longitude: 147°45.178' W
Easternmost Longitude: 147°45.178' W

Matanuska Glacier Till Sample 4:
Southernmost Latitude: 61°46.766' N
Northernmost Latitude: 61°46.766' N
Westernmost Longitude: 147°45.537' W
Easternmost Longitude: 147°45.1537' W

Caesar Till:
Southernmost Latitude: 40°4'2" N
Northernmost Latitude: 40°4'2" N
Westernmost Longitude: 83°00'25" W
Easternmost Longitude: 83°00'25" W

Parameter or Variable

This data set contains the results of laboratory experiments on shear stress and strain. Parameters include shear stress, shear strain, time, and layer thickness. Creep experiments were conducted under controlled shear stress to investigate the time-dependent deformational or creep behavior of till, with an inital layer thickness of 10 mm. Friction experiments were conducted with constant shear velocity, in order to find the shear strength and rate-dependent strength of till.

Parameter Description

Table 3. Parameter Description
Parameter Description
Creep Experiments
Shear Strain Shear strain, controlled in creep experiments.
Shear Stress (MPa) Shear stress, in megapascals (MPa)
Time Time in seconds
Friction Experiments
Rec Record number
Shear_str Shear strength, determined at a constant shear velocity
Shear_stress Shear stress, in megapascals (MPa)
Layer_thick Layer thickness, in micrometers (uM)
Norm_stress Normal stress, in megapascals (MPa)
Time Time in seconds
Friction Friction.

Sample Data Record


Sample data record from p538.txt. This sample shows only the first four records in the file.
rec shear_str Shear_stress layer_thick Norm_Stress Time Friction
0 0 0 2005 1.00E-07 1 0
1 0 0 2005 1.00E-07 11 0
2 0 0 2005 1.00E-07 21 0
3 0 0 10997 0.0026697 0 0

 

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

The total volume of this data set is 20.5 MB.

Software and Tools

Data are accessible using spreadsheet software. Image files may require image processing software.

Related Data Collections

4. Data Acquisition and Processing

Theory of Measurements

For detailed information on the experimental setup, data processing, and potential errors, see Rathbun et al., 2008.

5. References and Related Publications

Haefner, R. J. (Ed.) 1999. A conference on fractured glacial tills: Field trip guide to selected fractured glacial till sites and soils in central Ohio, paper presented at Water Management Association of Ohio Spring Conference on Fractured Glacial Tills, U. S. Geol. Surv., Columbus, Ohio, 10 May 1999 .

Rathbun, A. P., C. Marone, R. B. Alley, and S. Anandakrishnan. 2008. Laboratory study of the frictional rheology of sheared till. J. Geophys. Res., 113, F02020, doi:10.1029/2007JF000815.

The following related documents are available

Table 4. Related Documents
Document Description URL
Antarctic Glaciological Data Center (AGDC) Data Center Web site http://nsidc.org/agdc/

6. Document Information

Acronyms

The following acronyms are used in this document.

Table 5. Acronyms and Abbreviations
Acronym Description
EPS Encapsulated Postscript file
FTP File Transfer Protocol
MPa Megapascals
NSIDC National Snow and Ice Data Center
URL Uniform Resource Locator

Document Creation Date

12 April 2010

Document URL

http://nsidc.org/data/docs/agdc/nsidc0460_rathbun/index.html