EarthChem Portal Q&A

This page lists user-submitted questions and our answers. Submit a question to

Negative ages

Q: I am a regular user of the Earthchem portal. Just to inform you that I have noticed a "little bug". When you do any kind of query the min, max and mean age are sometimes negative in the resulting dataset... For instance, I have downloaded recently 350000 sample for various data (Sr, Rb...) and out of 350000 more than 5000 samples have negative age. It looks like some data entered are under the form 300 +-0.00345 and in this case when downloading the data the age return is -0.00345. Have you experience this issue before?

A:  Negative values represent a year age of a sample, instead of an MA representation. For example, a sample with an age of "-0.000065" would be 65 years old (at the time of publication). Most of these negative values come from NAVDAT and GEOROC and the ages come from a known eruption event.

Map polygon crossing 180 longitude

Q: I'm trying to enter a glossary entry so that I can easily search for data in the Aleutians. The draw polygon option cuts off the map at 180 long, so it doesn't include the entire area. If I try to enter the lat/long coordinates, it doesn't understand to continue across the 180 degree line. It tried to connect the polygon to the opposite side of the map across N America, Europe, Asia, etc. I have the same problem with New Zealand. I don't see a way to currently search Earthchem without splitting the entry into two polygons, which may cause duplicate or missing data from the search.

A: ***UPDATE*** The portal has been updated so that the map can scroll across the dateline now. ***  Original answer: Problems with crossing the 180 degree longitude line is a known issue on the polygon map, and we apologize for any frustration that it has caused. Unfortunately, the issue lies within the spatial software that we use, and there is no easy fix at this point. For the time being, the only workaround is to use two polygons as you suggest below. This issue is currently being investigated, and I will let you know as soon as a solution is available.

Pb: Isotope ratios

Q: Are the Pb isotope ratios accessible through earthchem raw ratios or age-corrected?

A: If the parameter name is appended by an (I) or (T), that means that the ratio is corrected for I = Initial age or T = age at time T (e.g. 50Ma). If the parameter name does not have any parenthetical appendix, then the author did not specify that the ratio was age corrected. In the PetDB database, if the parameter is appended by (T), there should be a comment in the methods section that indicates what the T time is.