Ghost Tree – a legacy of the 1964 Earthquake EarthCache

Portage Flats Ghost Tree – a legacy of the 1964 Earthquake

Welcome to the Alaska Wildlife Conservation Center (AWCC), who has graciously allowed this earthcache to draw attention to the Ghost Trees scattered across their facility at Portage. There is no container to find or logbook to sign. Your task is to locate answers on-site to questions about the geology of this location and the activity which occurred here impacting these trees, and to message your answers to the cache owner to demonstrate what you’ve learned during your visit.

The Alaska Wildlife Conservation Center (AWCC) is located on part of the original Portage townsite at the eastern head of Turnagain Arm (an elongated bay in the Upper Cook Inlet extending inland from the North Pacific Ocean). There is a fee to enter the grounds of this facility, currently at $15.00 per adult with discounts for seniors and children. The AWCC is a sanctuary dedicated to preserving Alaska’s wildlife through conservation, research, education and quality animal care. AWCC takes in injured and orphaned animals year-round and provides them with spacious enclosures and quality animal care. Most of the animals that arrive at the Center become permanent residents and will always have a home here. The Center maintains over 200 acres of spacious habitats for animals to feel at home and display their natural “wild” behavior. Visitors may see brown bears cooling off in the water, a bull moose strutting, wood bison roaming on pastures, free-ranging wolves, coyotes and more. Enjoy your visit here as you wander the entire grounds, but make sure you head to the Ghost Tree site first!

The 1964 Great Alaska Earthquake is the strongest ever recorded in North America, and its 9.2 magnitude is second worldwide only to the 1960 Chile quake measuring 9.5 in strength. The ground motion felt from the 1964 quake lasted from 3 to 5 minutes, depending on location. Its epicenter was located in Prince William Sound east of this site in Portage. As the quake occurred, residents of Portage experienced violent earth motion which caused multiple cracks to open in the terrain and geysers of water to shoot as much as 100 feet high. While no tsunamis swept down Turnagain Arm, the Portage townsite was flooded during Upper Cook Inlet’s next high tide.  It became rapidly apparent that Portage had subsided as much as ten feet below its previous elevation, causing flooding of the entire townsite at subsequent high tides. Today, super high tides still seep into the deeper three-feet-deep sections of drainage ditches found along the access road into the Alaska Wildlife Conservation Center property. Only the railroad and highway remained elevated above the tidal zone following the quake, and these transportation corridors suffered serious damage as well. Portage became uninhabitable, and its buildings were abandoned to weather away. Little is left of those structures, but the Ghost Forests remain.

This particular exhibit at the Alaska Wildlife Conservation Center (AWCC) was built to answer a persistent question asked by visitors – “why don’t you cut down all the dead trees scattered around here?”  As a conservation center, the AWCC purposes to maintain as much of the original landscape found in the old Portage townsite as possible while carrying out their support activities for wildlife. Across time since the 1964 earthquake, the dead trees have become useful in other ways to the birds and wildlife found here. Cutting the trees down just because they’re dead would impact those uses, and would remove a vivid reminder of how an earthquake can literally change the viability of the surrounding landscape for its residents.

As you examine the exhibits surrounding the ghost tree, you’ll find the information you need to answer seven of the questions below. Pay particular attention to the Ghost Forest and Tectonics signs as you formulate your answers (please make sure you don’t post photos of these signs in your logs, as their publication would result in your log being deleted). The final question requires you to consider what you’ve learned, and make a judgement call about what you’ve seen here.

Questions about Tectonics: 
1. The collision of what two tectonic plates occurs here?
2. At what speed and in what direction is the ‘diving plate’ moving?
3. What occurs between the two plates to trigger an earthquake?
4. What aspect of the quake’s depth created an enhanced impact?
5. What percentage of all the planet’s earthquakes occur in Alaska?

Questions about the Ghost Forests:
6. What killed the dead trees found here?
7. What aspect of how they died has resulted in the trees being preserved so well even as the human-built structures in the area have weathered away over the past 50+ years since the quake?

8. In your judgement, as you examine the trees still alive and growing around the AWCC property, how much subsidence in another earthquake do you think would be needed to kill the new growth you see happening here today?

Please message your answers to the cache owner to demonstrate what you’ve learned during your visit. Including photos in your log of the AWCC during your visit will help encourage others to come and learn about Alaska’s wildlife, tectonic forces, and the Ghost Forests (just don’t post photos of the exhibit signs, please!)

Operating Hours, Open Rain or Shine:

• January: 10 am to 3 pm (4-day operations: Friday, Saturday, Sunday and Monday)
• February: 10 am to 4 pm (4-day operations: Friday, Saturday, Sunday and Monday)
• March & April: 10 am to 5 pm
• May thru August: 8:30 am to 7 pm
• September: 9 am to 6 pm
• October: 10 am to 5 pm
• November: 10 am to 4 pm (4-day operations: Friday, Saturday, Sunday and Monday)
• December: 10 am to 3 pm (4-day operations: Friday, Saturday, Sunday and Monday)
• For Holiday Break we will be open 7 days a week from December 21 to December 31; we will be closed December 24, December 25 and January 1.
• CLOSED: Thanksgiving, Christmas Eve, Christmas Day and New Year’s Day.
• OPEN: All other holidays.

Note: Hours are subject to change without notice due to unforeseen circumstances.