Volcanic Hazards in the USA

Geol9 is exploring the volcanic hazards in different countries and their warning systems. I’ll be focusing on the US. After learning about tectonic plates, it is not surprise that all our volcanoes are aligned along the 'ring of fire' (except Hawaii as a hot spot).

There are several ways we minimize the danger of volcanic activity (apart from the obvious of ‘getting out of the way’…(J:

·         Forecasting (earthquakes as early warnings -although in 2014 a Japanese volcano erupted without any previous seismicity (livescience article), land swelling before eruption, gas emissions, etc.)

·         Volcanic Alert Codes (USGS): the levels of alert and the aviation code levels commonly change at the same time (chart on right). A non-erupting volcano will have a green icon, and a red one indicates an imminent eruption (see USGS Alert Codes).

Today (see image below) the US hazards map shows 5 volcanoes as to be above normal background (elevated unrest):

Cleveland, Mauna Loa, Pavlof, and Shishaldin Alert Level=ADVISORY. Aviation Color Code=Yellow. This means: “No eruptive activity detected; minor steaming from summit crater observed”.

Semisopochnoi Alert Level=WATCH. Aviation Color Code=Orange. This means: “Elevated seismicity throughout the week; no eruptive activity observed.”

USGS volcanic hazards 2/22/20

The best way to prepare is with education and if you live close to a volcanic mountain, be aware of it, be prepared, and listen to the authorities when evacuation is needed. 

Earthquake Hazards in the States

This week we are exploring earthquakes and what countries do to prevent/mitigate the hazard. If I want to know something about earthquakes in a place, the first websites I go to are: the USGS Real Time Earthquakes Website or the IRIS monitoring website.

Regarding where quakes are located in the US, this seismicity map (see image below from USGS) shows the (obvious, in hot pink) ring of fire portion on the West coast but also a central area in the middle of the plate. I’d like to talk a bit more about this non-obvious one. This area, called the New MadridZone was shaken by a M8(!) in 1811. The reason for the activity is a very old intraplate rift placed below the area (see image from http://showme.net).

The San Andreas Fault System is responsible for most of California natural quakes...we had over 550 in the last month...up north, the Cascadia Subduction Zone will be responsible for next big one that area has. So, at least we start to knwo the 'why' of these quakes.

Re: the 'what to do about it', apart from the obvious need for education, I want to focus on the USGS ShakeAlert system, developed for the West coast using some of the existing systems. Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of an EEW (Earthquake Early Warning) system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds, depending on the distance to the epicenter of the earthquake. 

A few seconds of warning could make all the difference (enough to stop transit/elevators and to drop, cover, hold on).

Being aware of the risk and know what to do when the shaking starts is very important. We know that earthquakes cannot be predicted [I recommend Dr. Jones’ book called the big ones’ if you want more information about that]

All for now-

Tectonic Setting and Natural Hazards-USA

This week we are exploring plate tectonics and how the location of each country is affected by its position respect to Earth's plate boundaries.

The USGS map below and this NOAA map shows clearly how the Easter US is a passive margin (aka, far away from a tectonic plate boundary) and the Western side of the country is a very active one, with the Pacific Plate, Cocos, Juan de Fuca plates connecting to the North American plate (plate tectonic boundaries). Not a surprise we are on the ‘Ring of Fire’, where a lot of the volcanic and seismic activity happens!

Of course, there are a few exceptions, like the geologic activity of Hawaii (hot spot) or the New Madrid area (ancient rift), both not at plate boundaries, but is for some other time.

We might not know when events like volcanic eruptions or big earthquakes will happen, but if you know your Tectonics, you definitely know where the do happen!

All for now-

Other Plate Maps found at USGS or Esri: interactive