Information presented on this website is considered public information (unless otherwise noted) and may be distributed or copied. Use of appropriate byline/photo/image credit is requested. We strongly recommend that USGS data be acquired directly from a USGS server and not through other sources that may change the data in some way. While USGS makes every effort to provide accurate and complete information, various data such as names, telephone numbers, etc. may change prior to updating. USGS welcomes suggestions on how to improve our home page and correct errors. USGS provides no warranty, expressed or implied, as to the accuracy, reliability or completeness of furnished data.

Some of the documents on this server may contain live references (or pointers) to information created and maintained by other organizations. Please note that USGS does not control and cannot guarantee the relevance, timeliness, or accuracy of these outside materials.

For site security purposes and to ensure that this service remains available to all users, this government computer system employs software programs to monitor network traffic to identify unauthorized attempts to upload or change information, or otherwise cause damage. Unauthorized attempts to upload information or change information on this website are strictly prohibited and may be punishable under the Computer Fraud and Abuse Act of 1986 and the National Information Infrastructure Protection Act. Information may also be used for authorized law enforcement investigations.

Links to Non-USGS Sites

Links and pointers to non-USGS sites are provided for information only and do not constitute endorsement, express or implied, by the USGS, U.S. Department of the Interior (USDOI), or U.S. Government, of the referenced organizations, their suitability, content, products, or services, whether they are governmental, educational, or commercial.

Non-Endorsement of Commercial and Other Non-USGS Products and Services

Hypertext links and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.

Content Accuracy, Completeness, and Usability of USGS Data and Information

We make every effort to provide and maintain accurate, complete, usable, and timely information on our web sites. However, some USGS data and information accessed through these pages may, of necessity, be preliminary in nature and presented prior to final review and approval by the Director of the USGS. These data and information are provided with the understanding that they are not guaranteed to be correct or complete. Users are cautioned to consider carefully the provisional nature of these data and information before using them for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences. Conclusions drawn from, or actions undertaken on the basis of, such data and information are the sole responsibility of the user.

Copyrights and Trademarks

USGS-authored or produced data and information are in the public domain. While the content of most USGS web pages is in the public domain, not all the information on our site is in the public domain. Some images/graphics are used by USGS with permission. For other uses, you may need to obtain permission from the copyright holder under the copyright law.

You are welcome to make a link to any of the Web pages USGS has published on the Internet. There is no need to request permission.

The USGS identifier is trademarked and must be used in accordance with the rules outlined at Visual Identity System. Information on who may use the USGS identifier and how to obtain a copy of it is available at Use of the Trademarked USGS Identifier by Outside Organizations.

We will identify material we use from sources outside of USGS, and request others do the same when using information published by USGS. Credit can be provided by including on the page (or via a link to a credits page) a citation such as:

Credit: U. S. Geological Survey
U. S. Geological Survey/photo by Jane Doe (if the artist is known)
USGS/Ft. Collins, CO (if originating office but not the artist is known)


Neither the U.S. Government nor any agency thereof, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights.