Tephrabase: Structure

Contents

1. Introduction 8. Radiocarbon Dating Table
2. Site Table 9. Historical Dating Table
3. Profile Table 10. Geochemical Table
4. Context Table 11. EPMA Session Table
5. Tephra Layer Table 12. Eruption Table
6. Tephra Subunit Table 13. Phase Table
7. Physical Property Table 14. Reference Table

1. Introduction

This database was developed in the Department of Geography at the University of Edinburgh (1994-1995). Both published and unpublished data on tephra deposits and their source volcanoes are available. Originally, Tephrabase only contained data on tephra layers erupted from Icelandic volcanoes; the database now also contains data on some tephra layers found in central Mexico and the Laacher See Tephra. The Mexican, Icelandic and Laacher See data is coded separately and searches on each area are carried out independently.

The tables detailed below describe the format of the main tables in the database and the type of information which is held in each. Where appropriate the maximum size of a column is shown. Each table actually contains more columns than are shown below, but these are only for controlling the structure of the database and creating links between tables. The column name within each table of the database are listed below in alphabetical order. Look up tables are not included in the list below.

Tephrabase ER Diagram

Riede, F., Bazely, O., Newton, A.J. and Lane C.S. (2011) A Laacher See-eruption supplement to Tephrabase: Investigating distal tephra fallout dynamics. Quaternary International 246(1-2), 134-144.

Newton, A.J., Dugmore, A.J. and Gittings, B.M. (2007) Tephrabase: tephrochronology and the development of a centralised European database. Journal of Quaternary Science 22, 737-743.

Newton A.J., Gittings B., Stuart N. (1997) Designing a scientific database Query Server using the World Wide Web: The example of Tephrabase. Innovations in GIS 4, Taylor and Francis, London, 251-266.

Newton A.J. (1996) Tephrabase. A Tephrochronological Database. Quaternary Newsletter, 78, 8-13.

2. Site Table

This table holds location data on a site. The site could be a site of an eruption, volcanic centre or profile where a tephra layer occurs.

Column Name Max. Length Description
Altitude   The altitude of the site in metres
Area 60 characters The area/region of a country the site is found in
Country 60 characters The country the sites is found in
Country/Ocean ID   Numerical value to identify counry/ocean/sea site is found in.
Grid Reference   The grid reference (8 figures) of the site (UK only)
Latitude   The latitude of the site
Longitude   The longitude of the site
Marine   Whether a site is terrestrial, lacustrine or marine
Site Name 60 characters The name of the site
Type Site   Whether the site is a type site for a tephra layer
Water Depth   Depth of water at a lacustrine or marine site

 

3. Profile Table

This table hold details about the profile where a tephra layer is found. The could be a core, ditch, archaeological site or even a surface.

Column Name Max. Length Description
Comment   Other information on profile
Profile Name 20 characters The name of the profile
Total Depth   Total depth of the profile in metres
Type of Profile   The type of profile (Russian core, ditch etc.)
Type Profile   Whether the profile contains a type tephra layer

 

4. Context Table

This table contains more information about a site or profile.

Column Name Max. Length Description
Summary 65.5 K characters More details about a profile or site.

 

5. Tephra Layer Table

This table hold details about the name and position of a tephra layer within a profile. Multiple names are available to accommodate the various names a tephra layer can be known as.

Column Name Max. Length Description
Bottom Depth   The depth of the base of a tephra layer in a profile I metres
Comment   Other information about the layer
Distance   Distance from vent (used by LST - can be calculated automatically)
Tephra Name 1 60 characters Formal name e.g. Hekla 4
Tephra Name 2 60 characters Regional Name e.g. Glen Garry Tephra
Tephra Name 3 60 characters Local Name
Tephra Name 4 60 characters Source Name
Thickness   Thickness of layer, rather than having upper and lower depth
Top Depth   The depth of the top of a tephra layer in a profile in metres
Type Tephra   Whether a tephra layer is a type tephra

 

6. Tephra Subunit Table

This table hold details of the name and position of subunits within a tephra layer. This would only be used in the case of macroscopic tephra layers.

Column Name Max. Length Description
Bottom Depth   The depth of the base of a subunit in a profile in metres
Subunit Name 1 60 characters Formal name
Subunit Name 2 60 characters Regional Name
Subunit Name 3 60 characters Local Name
Subunit Name 4 60 characters Source Name
Top Depth   The depth of the top of a subunit in a profile in metres
Type Tephra   Whether a subunit is a type subunit

 

7. Physical Property Table

This table hold details of the physical properties of a tephra layers.

Column Name Max. Length Description
% between 125-250 µ m   grain size
% between 250-500 µm   grain size
% between 500-1 µm/mm   grain size
% between 63-125 µm   grain size
% greater than 1 mm   grain size
% less than 63 µm   grain size
% Lithic   % of lithics in a tephra layer
% Glass   % of glass shards in a tephra layer
% Minerals   % of minerals in a tephra layer
Aggregate Tephra Colour 30 characters Hand specimen colour
Concentration 20 characters ? Concentration of shards per cm3?
Mean grain size   Mean grain size in mm
Median Grain Size   Median grain size in mm
Mineralogy 150 characters Mineralogy of tephra layer
Morphology 60 characters The morphology of the glass shards
Qualitative grain size 30 characters The qualitative grains size, e.g. coarse, fine etc.
RI Mean   The mean refractive index
RI Standard Deviation   The standard deviation of the refractive index to 1 sigma
Rounding 30 characters The amount of rounding of tephra grains
Shard Colour 20 characters The colour of the glass shards
Sorting 20 characters The degree of sorting ?
Tephra Layer Colour 30 characters The colour of the tephra layer insitu

 

8. Radiocarbon Dating Table

This table holds details on the radiocarbon dating of tephra layers, profiles and eruptions.

Column Name Max. Length Description
Address 200 characters The address of the radiocarbon laboratory
Bottom Depth   Depth of the base of a sample from a profile in metres
Conv/AMS   Whether a date was by beta counting (radiometric/ Conventional) or AMS
Delta 13C ratio   The measured ratio wrt PDB
Fraction 20 characters The fraction dated (e.g. humin, humic acid, cellulose, etc.)
Type of material 60 characters The material dated (e.g. peat, wood etc.)
Radiocarbon date   The mean age in conventional years BP
Sample lab. number 10 characters (e.g. GU-7115, SRR-5573, UB-3354)
Standard Deviation - 1   Standard deviation of the age measurement to 1 sigma
Top Depth   Depth of the top of a sample from a profile in metres

 

9. Historical Dating Table

This table hold details on the absolute, historical dating of an eruption or tephra layer

Column Name Max. Length Description
Bottom Depth   Depth of the base of a point in a profile in metres where the absolute date is known
End Date   The end date/time of an eruption or tephra fall in years AD/BC
Start Date   The start/time of an eruption or tephra fall in years AD/BC
Top Depth   Depth of the top of a point in a profile in metres where the absolute date is known

 

10. Geochemical Table

This table holds all of the geochemical data about a volcanic system, eruption or tephra layer. The columns in this table are arranged so that the major elements (wt %) are followed by the trace elements (ppm). Each of the major elements has an extra column which records the standard deviation of a mean.

Column Name Max. Length Description
Number of analyses   The number of analyses represented by a mean
Mean   Whether an analysis is a mean
Material   Material analysed (glass, plagioclase, pyroxene, biotite etc)
SiO2    
SiO2 Std Dev.   Standard deviation of a mean analysis
TiO2    
TiO2 Std Dev.   Standard deviation of a mean analysis
Al2O3    
Al2O3 Std Dev.   Standard deviation of a mean analysis
Fe2O3    
Fe2O3 Std Dev.   Standard deviation of a mean analysis
Fe2O3T   Total iron expressed as Fe2O3
Fe2O3T Std Dev.   Standard deviation of a mean analysis
FeO    
FeO Std Dev.   Standard deviation of a mean analysis
FeOT   Total iron expressed as FeO
FeOT Std Dev.   Standard deviation of a mean analysis
MnO    
MnO Std Dev.   Standard deviation of a mean analysis
MgO    
MgO Std Dev.   Standard deviation of a mean analysis
CaO    
CaO Std Dev.   Standard deviation of a mean analysis
Na2O    
Na2O Std Dev.   Standard deviation of a mean analysis
K2O    
K2O Std Dev.   Standard deviation of a mean analysis
P2O5    
P2O5 Std Dev.   Standard deviation of a mean analysis
LOI   Loss on ignition (XRF analyses only)
Total   The total of major elements (in XRF including LOI)
Total Std Dev.   Standard deviation of a mean analysis
Ba    
Ce    
Cl    
Cl Std Dev.    
Cr    
Cu    
F    
F Std Dev.    
La    
Nb    
Nd    
Ni    
Pb    
Rb    
Se    
Sr    
Th    
V    
Y    
Zn    

 

11. EPMA Session Table

This table hold details on the type of electron microprobe used for an analysis and the conditions it was operated under.

Column Name Max. Length Description
Accelerating Voltage   The accelerating voltage of the beam in kV
Beam Current   The beam current in nA
Correction Programme 20 characters The correction programme used (e.g. ZAF)
Counts   ?
Machine Name 60 characters The name and make of the machine used
Sample Type 60 characters The type of sample analysed (e.g. thin section - carbon coated)
Standards 60 characters The standards used to calibrate the machine
Type   WDS or EDS analysis
Beam Diameter   Diameter of electron beam in microns
Raster   whether beam was rastered or not
Comments   Further information about the EPMA analyses

 

12. Eruption Table

This table contains details of an eruption.

Column Name Max. Length Description
Eruption Name 60 characters The name of the eruption
Maximum Column Height   The maximum height of the column in metres
Mean Column Height   The mean height of the column in metres
Summary 65.5 K characters Summary information about an eruption
VEI   The VEI index of the eruption
Volcano/fissure 100 characters The name of the volcano/fissure
Volume of Lava DRE   The volume of lava produced - dense rock equivalent (km3)
Volume of Tephra DRE   The volume of tephra produced - dense rock equivalent (km3)
Volume Total DRE   The total volume of the eruption - dense rock equivalent (km3)

 

13. Phase Table

This table hold details of phases of activity during an eruption.

Column Name Max. Length Description
Maximum Column Height   The maximum height of the column in metres
Mean Column Height   The mean height of the column in metres
Phase Name 60 characters The name of the phase of activity
Summary 65.5 K characters Summary information about a phase of activity
VEI   The VEI index of the phase of activity
Volume of Lava DRE   The volume of lava produced - dense rock equivalent (km3)
Volume of Tephra DRE   The volume of tephra produced - dense rock equivalent (km3)
Volume Total DRE   The total volume of the eruption - dense rock equivalent (km3)

 

14. Reference Table

This table hold references on tephrochronology, volcanism and related topics. The references are at present very biased towards Iceland.

Column Name Max. Length Description
Address 180 characters The address of donators of unpublished data
Author 200 characters The authors of an article or book
Editor 60 characters The editors of a book
Journal 200 characters The title of a journal or book
Keywords 200 characters  
Name 60 characters The name of a donator of unpublished data
Page    
Publisher 60 characters The publisher of a book
Summary 65.5 K characters A summary of the reference
Title 240 characters The title of an article
Volume   The volume of a journal
Year   The year of publication
Weblink   URL of publication