Day 2 of the Atlantic Geoscience Society 36th Annual Colloquium at the Old Orchard Inn, Wolfville, Nova Scotia.
The sessions started at 8am and I kicked-off the day with a talk by Sheridan Thompson-Graham from Memorial University, Newfoundland.For her Masters she is looking at coastal erosion at Mistaken Point in Newfoundland. The site is now famous for the oldest occurrence of Ediacaran fossils for which UNESCO World Heritage status is being sought. However, the coastal site is eroding and the need to get a handle on the rates. As well as marine erosion processes, the site is affected by an increasing number visitors, and the attention of palaeontologists who have extracted some fossil specimens and taken casts of other. Sheridan's study is a good, but perhaps unusual, example of applied coastal geomorphology. There are some similarities with the Dorset Coast in the UK that has already attained World Heritage status based on its fossiliferous rocks.
I then sat in on a couple of talks that dealt with mass transport off the Scotian shelf. Grant Wach from Dalhousie University touched on this and noted mass wasting in submarine canyons, but Mike Giles in his talk suggested that most of these slope movement events are probably linked to seismic triggers. He cited the example of the 1929 Grand Banks slide that was triggered by an 7.2 magnitude earthquake that generated a tsunami that killed 28 people onshore in Newfoundland and Nova Scotia.
For the rest of the morning I participated on a session devoted to the Bay of Fundy. Elizabeth Kosters and Brian Todd introduced the session and explained that this was third of its kind (I was at the last one too at the AGS Colloquium in Dartmouth in 2008). Brian's talk concerned mapping the glacial history of the Bay, and is able to piece together ice retreat after the Last Glacial Maximum, including the role of sea-level in determing whether retreating glaciers were grounded or floated.
John Shaw of the Geological Survey of Canada gave an interesting talk on the late Holocene history of the Minas Basin at the head of the Bay of Fundy. He has evidence that the tidal range there expanded dramatically around 4000 years ago and believes the basin mouth was blocked by a gravel barrier that breached allowing a full connection with the main Bay. He also suggested that a local aboriginal Glooscap legend, that tells of a beavers dam being destroyed by a whale, may be an oral historical account of the event. The breaching of a barrier would certainly lead to flooding around the basin margins that would have displaced any settlements located there.
There followed a series of presentations on the topic of tidal power generation in the Bay of Fundy.David Greenberg, Richard Karsten, and Gordon Fader all talked on the topic. The idea of building tidal barrages in the Bay of Fundy has been tried with, at best, limited success (e.g. Annapolis Royal Barrage), but in some cases building causeways across estuaries has had negative impacts. For example, and for reasons other than power generation e.g. at Windsor, and Moncton on the Petitcodiac River, sediment infilling rapidly followed causeway construction.
Having abandoned the idea of tidal barrages, Nova Scotia is now in the process of deploying three seabed-mounted turbines, kind of like big submarine wind turbines. The first was deployed in November 2009 in the Minas Passage, so it'll be interesting to follow how they get on.
Richard presented figures that reinforce why considering harnessing tidal energy is so important. The current thinking is for between 200-1000 turbines to be deployed in the Minas Passage area, capable of generating between 0.2 and 2 GW. To put this in perspective, a nuclear power station generates around 2 GW (around the same as two traditional coal fired power stations)! So there is real potential here to make a major contribution from tidal power.
However, although 2-3 GW is the upper target for now, the Minas Passage has 6.9 GW of extractable energy, equivalent to 3.5 nuclear or 7 coal-fired power stations, but harvesting above 2-3 GW would start to seriously affect the natural tidal system. It must be noted that the tidal flow through the Minas Passage is extreme, being up to 1 million m3 per second! The Amazon River only discharges 220,000 m3/sec and the Mississippi 16,200, so the Minas Passage is exceptional.
Gordon then addressed some issues related to the installation of the turbines themselves, such as the unknown nature of the substrate of the Minas Passage and Channel (what will the turbines be anchored to?), the effect of tidal current scouring around the turbine footings, and the laying of expensive cables in relation to what appear to be slumps on the Passage margin.
The Bay of Fundy session was wrapped up with a paper on salt marsh sedimentation by Casey O'Laughlin, a student at St. Mary's University (who won a student prize later in the day), and my talk on student fieldwork in macrotidal environments. I used my teaching in the Severn Estuary in the UK as a case study, but made links with the Bay of Fundy.
Lunch followed with the Society's AGM. After that I took a look at some of the poster presentations, and there were some very good ones.Two caught my interest. The first by N. Crowell and others at Acadia University on processes along the coast near Antigonish in northern Nova Scotia, where examples of beach progradation (Pomquet Beach, up to 1.21 m/yr) and erosion (Dunns Beach, up to 0.6 m/yr) were presented.
Ian Spooner (Acadia Uni again) and others poster reviewed the occurence of mass wasting hazards in the Atlantic Canada region. Examples include 1) a debris flow at Harbour Breton on 1st August 1973 that wiped out several houses, killing 4 children; 2) a landslide at Daniel's Harbour on 15-20th April 2007 where houses fell off an eroding coastal cliff; 3) a cave-roof collapse at Ferryland in 1823 killing 42 fishermen; 4) an avalanche at Big Pond on 5th February 1856 where a snowlside buried a farm killing the family of 5 inside; and 5) a landslide in the Annapolis Valley at West Paradise in late April 2003.
The last couple of talks I saw were interesting. Rebecca Jamieson of Dalhousie University gave a talk a metamorphic aureole in Halifax. I had breakfast at Rebecca's table this morning and she explained that this research came about because the weather was too bad for her to take her students on a field trip, so she reverted to examining some outcrops on the Dalhousie campus, which threw up some surprising results. This is a great example of how teaching led to research, rather than the other way around as is normally the case.
Trevor Brisco and others from Acadia University finished the session with a controversial report on the discovery of possible impact craters in southern Nova Scotia. Ian Spooner and his colleagues had reported the finding of the Astrid crater a few years ago, and another impact-like structure was identified at Bloody Creek in 1987. The new study is of what appears to be a cluster of craters called the North Group (to the north of Bloody Creek). The area is now flooded by the Dalhousie Lake Reservoir, which hinders access to the landscape, but allows echo-sounding mapping from a boat.But air photos are available of the area before it was flooded. The granite surrounding the structure has been examined and shocked quartz appears to be present, leaving little doubt that the structure is an impact crater. The elliptical shape of the crater suggest that the bolide approached at a very low angle (<15 degrees), and must have exploded as an air burst above ground to produce the multiple craters seen in the vicinity. The Astrid crater was tentatively dated to 12,000 years, and could by a candidate for the Younger Dryas cooling event. Trevor also suggested that the North Group could be of this date, but added that the site, and the Bloody Creek structure, might have been ice covered at the time, reducing the impact on the landsurface. Of course, it could be older, but the feature is fresh enough to suggest a relatively recent date. If this is correct then the suite of craters in the area could be due to the progressive break up of a bolide on its low angled approach.
At the evening banquet I sat with Rob Fensome and his wife, Alan Ruffman, and Don Forbes. Rob and I discussed coordinating the writing of a report of the Teaching Evolution workshop for Atlantic Geology. And Alan, Don and I also talked about tsunami. After the Society prizes and the guest speaker, the traditional end of conference singalong was a good way to wind down. Overall, an excellent conference and well worth the trip.