New Release – AZGS Guides to Northern Arizona Geology

The Arizona Geological Survey has just released an electronic version of a classical work for free download: “Geology of Northern Arizona – with notes on archaeology and paleoclimate” http://repository.azgs.az.gov/uri_gin/azgs/dlio/1647

This is a two-volume set originally published in 1974, contains about 800 pages. Here are the contents:

Volume 1
Geology of northern Arizona with notes on archaeology and paleoclimate, pt. 1, Regional studies p. 1-407

PRECAMBRIAN GEOLOGY

A preliminary report on the older Precambrian rocks in the upper Granite Gorge of the Grand Canyon

Preliminary report on the Unkar Group (Precambrian) in Grand Canyon, Arizona

The late Precambrian Chuar Group of the eastern Grand Canyon

Upper Precambrian igneous rocks of the Grand Canyon, Arizona

Rb-Sr age of the Cardenas Lavas, Grand Canyon, Arizona

Precambrian polar wandering from Unkar Group and Nankoweap Formation, eastern Grand Canyon, Arizona

PALEOZOIC GEOLOGY

Paleozoic rocks of Grand Canyon

The Toroweap Formation: A new look

MESOZOIC GEOLOGY

Mesozoic stratigraphy of northeastern Arizona

Mesozoic vertebrates of northern Arizona

CENOZOIC GEOLOGY, PALEOCLIMATE, AND ARCHAEOLOGY

K-Ar chronology for the San Francisco volcanic field and rate of erosion of the Little Colorado River

Cenozoic volcanism and tectonism of the southern Colorado Plateau
Southwest paleoclimate and continental correlations

A resume of the archaeology of northern Arizona

STRUCTURAL GEOLOGY

Synopsis of the Laramide and post-Laramide structural geology of the eastern Grand Canyon, Arizona

Structural evolution of northwest Arizona and its relation to adjacent Basin and Range province structures

The Bright Angel and Mesa Butte fault systems of northern Arizona

ECONOMIC GEOLOGY

Review of the development of oil and gas resources of northern Arizona

Volume 2:
Geology of northern Arizona with notes on archaeology and paleoclimate, pt. 2 Area studies and field guides

GRAND CANYON

River guide of Colorado River–Lee’s Ferry to Phantom Ranch

Kaibab trail guide to the southern part of Grand Canyon, northern Arizona

NORTH-CENTRAL ARIZONA

Geologic resume and field guide, north-central Arizona

Interference and gravity tectonics in the Gray Mountain area, Arizona

Geology of Shadow Mountain, Arizona

SAN FRANCISCO VOLCANIC FIELD

Geo1ogy of the eastern and northern parts of the San Francisco volcanic field, Arizona

Field guide to the geology of the San Francisco volcanic field, Arizona

Geology of the Elden Mountain area, Arizona

Xenoliths of the San Francisco volcanic field, northern Arizona

SAN FRANCISCO MOUNTAIN

The volcanic history of the San Francisco Mountain, northern Arizona

Glacial and pre-glacial deposits in the San Francisco Mountain area, northern Arizona

Field guide to the geology of the San Francisco Mountain, northern Arizona

Phreatomagmatic deposits of the Sugarloaf tephra, San Francisco Mountain, northern Arizona

Preliminary geochemical study of the lava flows of Humphrey’s Peak, San Francisco Mountain, northern Arizona

VERDE VALLEY–HACKBERRY MOUNTAIN AREA

Miocene-Pliocene volcanism in the Hackberry Mountain area and evolution of the Verde Valley, north-central Arizona

Paleontology, biostratigraphy, and paleoecology of the Verde Formation of Late Cenozoic age, north-central Arizona

Field guide for southeast Verde Valley–northern Hackberry Mountain area, north-central Arizona,

HOPI BUTTES–NAVAJO BUTTES AREA

The geology of Hopi Buttes, Arizona

The Buell Park kimberlite pipe, northeastern Arizona

Field guide for Hopi Buttes and Navajo Buttes area, Arizona
BLACK MESA AREA

Field guide for the Black Mesa–Little Colorado River area, northeastern Arizona

Ground water in the Navajo Sandstone in the Black Mesa area, Arizona

Paleoenvironmental and cultural changes in the Black Mesa region, northeastern Arizona

JEROME AREA

Economic geology and field guide for the Jerome district

Other new releases:

GEOLOGIC HAZARDS IN ARIZONA
AZGS FIELD GUIDES TO ARIZONA GEOLOGY

The Measure of an Earthquake

We heard that the recent Japanese earthquake measured 8.9. What does that number mean? The number used to refer to the Richter Scale, but now refers to the moment magnitude scale, but the numbers are calculated so that they are the same in both scales. The moment scale measures the size of an earthquake in terms of the rigidity of the earth, the amount of movement and the size of the area affected. In other words, the amount of wiggle on a seismograph. Both the Richter and moment scales are logarithmic, meaning that an earthquake of size 7 is 10 times stronger than an earthquake of size 6. But the amount of energy released is another matter.

Lee Alison, Arizona State Geologist, explains on his blog:

How does the Japan earthquake of magnitude 8.9 compare to other recent large quakes?

The news media do a better job than they used to of noting that each magnitude number is 10 times that of the lower number. But most everyone assumes that refers to the relative amount of energy released by the quake – comparable to measuring the power of atomic bombs for instance.

Not true.

The magnitude is a measure of the amplitude of the seismic waves. But each 1.0 magnitude increase is equal to approximately a 32 times increase in energy release. Each increase of magnitude by 2.0 equals 32 x 32 or (about) 1,000 times increase in energy released.

The M8.9 Japan quake released the equivalent of 336 megatons of TNT. In comparison, last month’s Christchurch, New Zealand M6.3 quake was equal to 43 kilotons, and last year’s M7.0 Haiti quake was equal to 474 kilotons.

The Japan quake was about 7814 times bigger than the Christchurch quake and 709 times larger than the Haiti quake.

I’ve simplified this in regards to Richter magnitude vs moment magnitude but my intent is to emphasize the power of the Japan quake.

 The strongest recorded earthquake was in Valdivia, Chile, May 1960. It measured 9.5. The second largest, measuring 9.2, was in Alaska in 1964. The 1906 earthquake in San Francisco had a moment magnitude of 7.9. The U.S. Geological Survey says that an earthquake of about 8.0 or more occurs on average of once per year.

The Alaskan earthquake is interesting because it demonstrated a certain property of some clays that contributed to the extensive damage in Anchorage. Some clays are thixotropic, meaning that when subject to shear stress, that is, you shake them, they turn to liquid. Thixotropic substances are normally thick and viscous, but turn very liquid under shear stress. You have experienced thixotropy with a ketchup bottle.

Besides shaking and breaking, seismic sea waves, tsunamis, are the greatest danger. Tsunamis are long-wavelength ocean waves with energy extending from the sea surface to the ocean floor. When the wave reaches shallow water near the coast, all that energy is concentrated into a smaller and smaller space, hence its destructive force. In mid-ocean, a tsunami is barely noticeable.

You can see a list of the largest recorded earthquakes here.

Most earthquakes occur near the edges of tectonic plates, but there are some intra-plate quakes as well. For instance, on December, 16, 1811, a large earthquake, estimated strength 7.2-8.1, occurred near New Madrid, Missouri. New York is not immune to earthquakes either. See here for earthquake information by state.

 And some earthquakes are caused by human intervention. I experienced the Denver earthquakes of 1967-1968. The Rocky Mountain Arsenal near Denver was disposing of waste material by pumping it down more than 12,000 feet beneath the surface. That lubricated a deep range-front fault and caused is to slip.

 Here is a map from the US Geological Survey showing locations of major earthquakes since 1900. The pattern describes the boundaries of major tectonic plates and the volcanoes of Hawaii.