Accretionary Wedge #25: An Illustrated Glossary of Cool Geological Things

A post by Chris RowanA post by Anne JeffersonWelcome to the latest edition of the Accretionary Wedge geoblogging carnival. We’ve been delighted by the response to our call for your favourite geological imagery, and the number of nominations we’ve received has been matched by their diversity – images have ranged from the microscopic to continental scales, from the depths of geological time to the present day, from the igneous to the sedimentary. The only way we could think of to do this smorgasboard of earth science justice was in the form of a visual dictionary, matching the images you’ve provided to the feature or process that they exemplify. Clicking on each image will allow you to see it in all its full-resolution glory at the original post, which in many cases also provides some more background on the geological feature or process depicted. Fun, pretty and at least a little bit educational – we hope you’ll have as much fun looking through our little glossary as we had putting it together.

A

Arch, natural – Formed by differential erosion at the base of a narrow ridge.

Photo: Arch, Arches National Park from Geotripper

Geotripper.jpg

B

Beach – deposit of unconsolidated sediment (sand, gravel, or shell fragments) at the land-water interface. One of many coastal zone morphologies.

Photo: Unknown beach with channel deposits. From Michael Welland.

Sandglass.jpg

GeoSciBlog breccia.jpg
Breccia – coarse sedimentary or volcanic rock with angular clasts

Photo: Pyroclastic breccia, Eagle Mtns, west Texas. From geosciblog.

Butte – prominent, isolated hill with steep sides and flat top. Smaller than a mesa.

Photo: Monument Valley by Dino Jim.

Dino Jim Mon Valley.jpg

C

Canyon (or gorge) – a deep, steep-sided valley, often formed by a river incising into a plateau or mountain range.

Photo: Canyonlands National Park from Geology Happens

Geology Happens.jpg

ebb tidal delta.jpg
Coastal zone – region where interaction of terrestrial and marine processes occurs. Morphology can take the form of a beach, barrier island, delta, cliff, or wave-cut platform.

Photo: Ebb-tidal delta – eastern Brazil. From Geologia Marinha e Costeira.

Conglomerate – coarse sedimentary rock with rounded clasts.

Photo: Ogallala/Arikaree formation near the Pawnee Buttes in north eastern Colorado (conglomerate butte landscape) from Russ Dale

Dale Cong.jpg

D

Debris flow – type of mass wasting where large clasts are carried in a mud-water mixture.

Photo: Debris flows, Pacific NW. From Anne Jefferson

Debris flow.jpg

PoolsRiffles.jpg
Dessication cracks – fractures formed by the shrinkage of clay, silt, or mud as it dries out from subaerial exposure.

Photo: Riviere de Terre – natural ‘artwork’ featuring dried, cracked clay. From Pools and Riffles.

Diagenesis – post-depositional alteration of sediments at low temperatures and pressures, often leading to the growth of new minerals in response to changing geochemical conditions.

Photo: pendant calcite crystals precipitated within meteoric aquifers during late Ordovician sea-level fall, Appalachians. From Suvrat.

Suvrat.jpg

Taconic.jpg
Differential weathering – divergence in the degree of weathering and erosion of different lithologies exposed to the same environment. Differential weathering is a factor in the formation of arches, buttes, and mesas, as well as steep slopes where some layers form vertical cliffs and other rock layers have subvertical exposures.

Picture: Letchworth State Park in Castille, NY, painted by Levi Wells. From John van Hoesen.

E

Exposure – the amount of geology that is exposed on the surface, and not hidden by pesky vegetation, soils, etc.

Photo: Cerro Divisadero, Patagonia, from Brian Romans

BrianR Patagonia.jpg

Olelog KT.jpgGeology Blues KT.jpg
Extinction event – abrupt disappearance of species, often as a result of extreme environmental changes, which can also result in a prominent lithological boundary. Significant (mass) extinction events include:

- K/T (or K/Pg) boundary, 65 million years ago

Photos: (top) KT boundary at Stevns Klint in Denmark. From olelog.

(bottom) KT boundary, Makoshika State Park, Montana. From Geology Blues

- Permo-Triassic boundary, 250 million years ago.

Photo: Permo-Triassic transition, Dolomites, N Italy. From Nologic.

Nologic.jpg

F

Folding – deformation of formerly horizontal layers of rock, usually due to compression.

Photo: Kings Canyon National Park. From Helena Heilotrope

Folding.jpg

Failed Rift Lamurde.jpg
_, plunging – non-horizontal fold axes, due to later deformation events.

Photo: Lamurde Anticline, from Failed Rift.

_, ptygmatic – occurs in sequences with high viscosity contrasts between layers.

Photo: ptygmatic folding in metagraywacke, from Callan Bentley.

Callan.jpg

Overturn.jpg
_, overturned, recumbant – where high deformation leads to inversion of stratigraphy in fold limbs.

Photo: overturned syncline at Dog Canyon, Big Bend National Park. From Antonio

G

Gooseneck – the pinched bit of land in an extremely bowed stream meander.

Photo: Goosenecks, Utah. From Failed Rift.

Failed Rift Goosenecks.jpg

GeoFroth GCanyon Rain.jpg
Gullywasher – an intense rainstorm that activates ephemeral channels.

Photo: the most epic rainstorm of Kyle House’s life.

H

Hematite – iron oxide (Fe2O3), a common product of weathering and other low temperature alteration.

Photo: Hematite sheets, Red River Gorge, Kentucky. From Stubotics

stubonics.jpg

J

Jointing – rock fractures with no displacement across the fracture. Can be the result of regional stresses or cooling of volcanic rock.

Photo: Long’s Peak, from Pascal

Pascal Longs Peak.jpg

K

Kyanite – an aluminum-rich silica mineral (Al2SiO5), commonly deep blue in color, that generally forms during high pressure metamorphism.

Photo: Metamorphic kyanite, Scotland. From Life-Long Scholar

LLScholar Kyanite.jpg

L

Landslide dam – formed when a landslide blocks a river valley, these natural dams impound water upstream. Such dams can create hazards if the upstream impounded water floods property or if they suddenly overtop or breach releasing a flood wave downstream.

Photo: Attabad landslide, Hunza, N. Pakistan from Dave’s Landslide Blog

Landslide dam.jpg

Erte_Ale_1.jpg
Lava Lake – body of mostly molten lava contained within a depression over a volcanic vent.

Photo: Erta Ale, Afar, Ethiopia from Chris Rowan

M

Mesa – tableland with steep sides and flat top of uplifted, erosion-resistant rock. A mesa is generally larger than a butte.

Photo: North Caineville Mesa, just east of Capitol Reef National Park in southern Utah. From Jim Repka.

Repka Mesa.jpg

Lockwood.jpg
Mountain – the natural habitat of the geologist.

Photo: Ansel Adams, Winter Sunrise, Sierra Nevada. From Lockwood.

O

Ooids – round, concentrically layered sedimentary grains, usually of calcium carbonate.

Photo: Photomicrograph of ooids in a Jurassic carbonate, from Lost Geologist

LostGeo.jpg

LfDetach Gold.jpg
Ore – rocks containing high concentrations of economically useful minerals.

Photo: Gold with naumannite (Ag2Se), Northern Nevada. From Silver Fox.

P

Pioneer Species – the first organisms to colonise bare land, either newly created or swept clean by fire or flood.

Photo: First colonisation of lava flow by plant from Magma Cum Laude.

Magma Cum Laude.jpg.

mantle-zoom.jpg
Power Law Creep – a type of deformation where small increases in applied stress leads to greatly increased strain rates. Thought to control deformation in the mantle explaining how you can get extremely rapid mantle flow around subducting slabs.

Picture: model of mantle flow around subducting Alaskan slab, from Discovery News.

Precipice – often encountered by single minded geologists in search of the perfect outcrop.

Photo: from Kyle House.

GeoForth Snake Cliff.jpg

S

Seismic Reflection Survey – controlled release of sound waves to examine the subsurface structure of the Earth. Modern computer processing provides extremely high spatial resolution.

Photo: Buried paleo-channels in Gulf of Mexico. From Hindered Settling.

HindSett Sesimic1.jpg

seismogram.jpg
Seismogram – a visual record of ground motions due to an earthquake.

Photo: Seismograph for Mb 6.0 earthquake beneath the Kermadec Islands on Sept 21, 1981, recorded at Adelaide, Australia. From Hypocentre.

T

Tilting – regional deviation of beds away from the horizontal, usually in response to regional tectonic uplift.

Photo: Tilted sandstones, Fountain Valley, Roxborough State Park near Denver, Colorado. From Russ Dale

Dale sst.jpg

Geoberg.jpg
Twinning – where a crystal is subdivided into regions with different lattice alignments.

Photo: twinned selenite (sparry gypsum), from Lutz.

V

Volcano – an opening in the Earth’s surface through which lava, ash, or gases are erupted. Volcanoes chiefly occur in regions where rifting, subduction, or hot spots have triggered melting of the mantle.

Photo: Mt St Helens – volcano above a subduction zone. From Short Geologist.

Short Geologist Mt St Helens.jpg
Eyjafjallajokul.jpg
Photo: Eyjafjallajokull, Iceland – volcano at a rift zone from Eruptions.

Categories: geology, photos
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Comments (25)

  1. What a great collection!

  2. KJHaxton says:

    Fantastic photos!

  3. Kim Hannula says:

    Fantastic job. Great pictures, great organization.
    Can I make a pedantic terminology request? I would like the term “recumbent” used in the description of the overturned fold, in hopes that this post will turn up in Google image searches. (Yes, the fold is also overturned, but I’ve found that students tend to assume that a map symbol for an overturned fold means something like that fold, even if the dip symbols should tell them that one of the limbs of the fold is just barely overturned.)
    The images are gorgeous. Great idea for an AW.

  4. Philip says:

    I love how you organized the photos

  5. What a lovely turn-out to the quest of the ultimate image!

  6. ed says:

    This is awesome. Thanks so much for hosting and organizing a wonderful assemblage of images. I needed a new alphabet book and now I have one. Thanks again!

  7. Kyle House says:

    Very nice execution of this idea!

  8. Lockwood says:

    What a terrific edition! Thanks!

  9. Pascal says:

    Excellent collection :)

  10. jim repka says:

    The photos are lovely as is the organization! It’s going to take me several days to work my way through all of the posts…

  11. Jim Lehane says:

    I was wondering how you would organize such a motley collection of photos and I must say you have done a superb job. A+

  12. Amber S says:

    Beautiful pictures and great collection of geology terms! I especially liked the Pioneer Species photo. Tenacious little plants.
    This post should have a prominent place in your sidebar. Like under Super Cool Posts (or something, I’m sure you can do better than that :-) )

  13. EffJot says:

    I completely missed this Accretionary Wedge’s call and deadline. :-(
    But looking at all these are really great photos, I couldn’t find much in my own pictures to match. However, some time ago I have photographed a nice fold in southern Germany, and written a post about it; but it’s not fully translated yet. (The pictures are there, of course.)

  14. suvrat says:

    thanks a lot for this edition of the wedge… great presentation.

  15. Lab Lemming says:

    So do we need to fill in the missing letters?

  16. Vicki says:

    Nice!
    I think this is the first ScienceBlogs post I’m bookmarking.

  17. Ikenna says:

    Awesome wedge!

  18. Ann says:

    I can’t believe you didn’t have a ‘R’ for Rocks or other ‘r’ words like river or ridge. But I love what you did with the pictures and letters you did use. You should pat yourselves on your back for doing such a great job. Thanks for taking the time and effort to do such a wonderful job.

  19. parclair says:

    I really like this format– a picture related to the link, it helps me sort out that which I’d like to explore. Perhaps in the future, all your AW’s could contain a picture as well as a few lines from the article? Thanks, I really enjoy your blog.

  20. ontherocks says:

    A very enjoyable array of geophotos.

  21. Andrew says:

    I have filled in the rest of the alphabet here on my About.com site.

  22. Silver Fox says:

    Not very many letters missing, considering that we weren’t given the assignment of filling up the alphabet. Nice glossary, great Wedge!

  23. Earl R. Verbeek says:

    Wonderful photos, great collection — nice to stumble upon this as a resource. If I may, a quibble: under the letter J, jointing is a process, and joints the result. The photograph shows the latter.

  24. Cheryl Ann says:

    Very interesting and informative collection of photos! What a great idea!