Skip to main content

pressure shadow

pressure shadow The area in a regional metamorphic rock which is protected from deformation by the presence of a relatively rigid porphyroblast or porphyroclast. Randomly orientated quartz and/or chlorite concentrates in triangular regions next to the faces of the porphyroblast or porphyroclast which are themselves orientated perpendicular to the schistosity of the surrounding, deformed, metamorphic fabric. During metamorphism and deformation quartz and chlorite are dissolved from the region of high pressure, where the matrix is squeezed against the hard, unyielding porphyroblast or porphyroclast, and are redeposited in the no-stress shadow region on either side of the porphyroblast where the deformed fabric wraps around the crystal, so forming the pressure shadow.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"pressure shadow." A Dictionary of Earth Sciences. . 15 Sep. 2019 <>.

"pressure shadow." A Dictionary of Earth Sciences. . (September 15, 2019).

"pressure shadow." A Dictionary of Earth Sciences. . Retrieved September 15, 2019 from

Learn more about citation styles

Citation styles gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, cannot guarantee each citation it generates. Therefore, it’s best to use citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

The Chicago Manual of Style

American Psychological Association

  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.