Tephrabase: Structure
Contents
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 Both published and unpublished data on tephra deposits and their source volcanoes are available.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.
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 Description | 400 characters | Characteristics of the layers: e.g. Fine grained black tephra |
| 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 |