Taylor Planz: Surveying 101, July 18, 2018


 

NOAA Teacher at Sea
Taylor Planz
Aboard NOAA Ship Fairweather
July 9 – 20, 2018

 Mission: Arctic Access Hydrographic Survey
Geographic Area of Cruise: Point Hope, Alaska and vicinity
Date: July 18, 2018 at 10:15am

Weather Data from the Bridge
Latitude: 66° 24.440′ N
Longitude: 163° 22.281′ W
Wind: 17 knots SW, gusts up to 38 knots
Barometer: 758.31 mmHg
Visibility: 5 nautical miles
Temperature: 12.2° C
Sea Surface 9.6° C
Weather: Overcast, no precipitation

Science and Technology Log

NOAA Ship Fairweather has a variety of assignments in different parts of the west coast each year, mostly in Alaska. They also work with many different organizations. In April of 2018, the US Geological Survey, or USGS, hired the ship to complete the last part of the survey of a fault line, the Queen Charlotte Fault, which lies west of Prince of Wales Island, Alaska. This was a joint venture between the US and Canada because it is the source of frequent and sometimes hazardous earthquakes. The Queen Charlotte Fault lies between the North American Plate and the Pacific Plate. The North American Plate is made of continental crust, and the Pacific Plate is made of oceanic crust. The two plates slide past one another, so the plate boundary is known as a transform, or strike slip, fault.

Queen Charlotte fault area

This image is from the USGS, who have been surveying the Queen Charlotte Fault area for many years. Photo Source: https://soundwaves.usgs.gov/2016/01/

The image to the right came from the USGS. Notice the two black arrows showing the directions of the North American and Pacific plates. Strike slip faults, such as this one, have the potential to produce damaging earthquakes. The San Andreas Fault in California is another example of a strike slip fault. The Queen Charlotte Fault moves relatively fast, with an average rate of 50 mm/year as shown in the photo. The USGS explains the Queen Charlotte fault beautifully in this article.

The image below was created after hydrographers on NOAA Ship Fairweather processed the data from their survey in April. The colors show relative depth across the fault, with red being the shoalest areas and blue being the deepest areas. In the top right section, you can see Noyes Canyon. There are many finger-shaped projections, which are result from sediment runoff. Notice that the color scheme in this area does not have much orange or yellow; it basically goes from red to green. If you were to look at this map in 3-D, you would see in those areas that the sea floor dramatically drops hundreds of meters in a very short distance.

Queen Charlotte Fault and Noyes Canyon

Queen Charlotte Fault and Noyes Canyon. Photo Courtesty of HST Ali Johnson

It is also worth noting what can be found in the remainder of this image. When NOAA finishes their survey, two different products are formed. The first is the colored map, which you see to the far left of the image. This is useful for anyone interested in the scientific components of the area. Mariners need the information as well, but a colored schematic is less useful for marine navigation, so nautical charts are produced (or updated) for their use. A nautical chart looks just like the remainder of this image. Small numbers scattered all over the white part of the map (ie – the water) show the depth in that area. The depth can be given in fathoms, meters, or feet, so it is important to find the map’s key. The purpose of the charts is to communicate to mariners the most navigable areas and the places or obstacles that should be avoided. The nautical charts usually have contour lines as well, which give a better picture of the slope of the sea floor and group areas of similar depth together.

Lower half of Queen Charlotte Fault, photo courtesy of HST Ali Johnson

Lower half of Queen Charlotte Fault, photo courtesy of HST Ali Johnson

The photo above is a closer view of the Queen Charlotte Fault. Can you see the fault? If you cannot see it, look at the line that begins in the bottom center of the photo and reaches up and to the left. Do you see it now? On the left side of the fault lies the Pacific Plate, and on the right side lies the North American Plate. If you look even closer, you might find evidence of the plates sliding past each other. The areas that resemble rivers are actually places where sediment runoff imprinted the sea floor. If you observe closely, you can see that some of these runoff areas are shifted at the location of the fault. Scientists can measure the distance between each segment to determine that average rate of movement at this fault line.

I also wanted to briefly mention another small side project we took on during this leg. A tide buoy was installed near Cape Lisburne, which is north of Point Hope. The buoys are equipped with technology to read and communicate the tidal wave heights. This helps hydrographers accurately determine the distance from the sea surface to the sea floor. The buoy will remain at its station until the end of the survey season, at which time it will be returned to the ship.

 

 

Personal Log

Northwest Alaska may not be a breathtaking as Southeast Alaska, but it has sure been an interesting trip! It amazes me that small communities of people inhabit towns such as Nome, Point Hope, and Barrow (which is about as far north as one can travel in Alaska) and endure bone-chilling winter temperatures, overpriced groceries, and little to no ground transportation to other cities. Groceries and restaurant meals are expensive because of the efforts that take place to transport the food. During my first day in Nome, I went to a restaurant called the Polar Cafe and paid $16 for an omelette! Although the omelette was delicious, I will not be eating another during my last day in Nome on Friday. It is simply too expensive to justify paying that much money. I also ventured to the local grocery store in hopes of buying some Ginger Ale for the trip. Consuming ginger in almost any form can help soothe stomach aches and relieve seasickness. Unfortunately ginger ale was only available in a 12-pack that happened to be on sale for $11.99. I decided to leave it on the shelf. Luckily the ship store has ginger ale available for purchase! The ship store is also a great place to go when your sweet tooth is calling!

The Ship Store

The Ship Store opens most nights for personnel to buy soda, candy, or even t-shirts!

 

Did You Know?
The Queen Charlotte fault was the source of Canada’s largest recorded earthquake! The earthquake occurred in 1949 and had a magnitude of 8.1!

Question of the Day
As mentioned above, northern Alaska reaches temperatures colder than most people can even imagine! Nome’s record low temperature occurred on January 27, 1989. Without using the internet, how cold do you think Nome got on that day?

Answer to Last Question of the Day:
How does a personal flotation device (PFD) keep a person from sinking?

When something is less dense than water it floats, and when it is more dense than water it sinks. Something with the same density as water will sit at the surface so that it lies about equal to the water line (picture yourself laying flat on the surface of a lake). Your body is over 50% water, so the density of your body is very close to the density of water and you naturally “half float”. A PFD, on the other hand, is made up of materials which have a lower density than water and they always float completely above water. When you wear a PFD, your body’s total density is a combination of your density and the PFD’s density. Therefore, the total density becomes less than the density of water, and you float!

Sources:
Danny, et al. (2016). Investigating the Offshore Queen Charlotte-Fairweather Fault System in Southeastern Alaska and its Potential to Produce Earthquakes, Tsunamis, and Submarine Landslides. USGS Soundwaves Monthly Newsletter. https://soundwaves.usgs.gov/2016/01/.

Torresan, L (2018). Earthquake Hazards in Southeast Alaska. USGS Pacific Coastal and Marine Science Center. https://walrus.wr.usgs.gov/geohazards/sealaska.html.

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s