Geology and Sea Level Change

Examples of the different volcanic flow units and evidence of past higher sea-levels and possible future sea-level rise impacts



Tim Webster, PhD

Applied Geomatics Research Group

COGS, Middleton

timothy.webster@nscc.ca

825 5475



The North Mountain is comprised of three volcanic flow units and was erupted from fissure volcanoes during the Triassic period, 200 Million Years ago. The three volcanic flow units are quite distinct and have variable resistance to erosion. As a result the morphology (shape) of the North Mountain reflects these differences in erodability of the flow units. The lower flow unit (oldest) is exposed along the south face of the North M Mountain and is quite thick, massive with columnar joints and very resistant to erosion. The resistance to erosion of this unit is in part why we have such a steep slope on the north side. The lower flow unit is overlaid by the Middle Flow unit which is comprised of several thin volcanic flows that are highly vesicular (gas bubbles). These air bubbles have been subsequently in filled with zeolite minerals as a result of ground water circulation through the rocks. Stilbite, Nova Scotia’s mineral, is one such mineral that infill’s these voids in the rocks. Zeolites have a unique crystal structure and grow radially outward. The Middle Flow unit is less resistant to erosion and is often referred to as “rotten rock” by local construction operators. The Upper Flow unit overlies the Middle Flow Units and is similar to the lower flow unit in that it is resistant to erosion and often outcrops along the Bay of Fundy Coast.



The flow units have been mapped with the aid of a new remote sensing technique known as LiDAR, Light Detection & Ranging. We use a laser onboard an aircraft to precisely measure the earth’s topography (lay of the land) to an accuracy of 15 cm in the vertical. The measurements are then used to construct a continuous surface known as a Digital Elevation Model (DEM). We then use these DEM in the computer to better visualize the subtle topographic changes of the land surface. As a result we can see the contacts between the flow units and other interesting landforms including raised terraces along the Bay of Fundy that represent higher sea-levels. After deglaciation 12-15,000 years ago, the sea-level rose faster than the earth’s crust rebounded. Evident of this high sea level is found at several locations along the coast in the form of terraces. Recent tide gauge records from Saint John, NB indicate relative sea-level is rising by 22 cm per century. This is a combination of crustal subsidence and global sea-level rise. We have also used these new LiDAR elevation models to map the town of Annapolis Royal and project possible flood limits based on storm surges and future projections of higher sea-levels. The Groundhog Day storm of 1976 was used a bench mark storm and the flood extent was mapped using the LiDAR DEM. Future sea-level rise projections were then used with this storm to predict what areas are at risk if the storm were to reoccur in the future.



The field trip will begin with a presentation of the sea-level history of the area, followed by an explanation of LiDAR and the improvements to topographic mapping that it provides. Flood maps of Annapolis Royal during the Groundhog Day storm and possible future flooding considering sea-level rise will be shown. Maps of the North Mountain will be displayed and the contact between the flow units identified. In addition we will examine these raised beach terraces that have resulted from past higher sea-levels. We will then depart to visit the different volcanic flow units and contacts in the field and the raised terraces along the coast.


Tim Webster, Ph.D.
Research Scientist, Applied Geomatics Research Group (AGRG)
Centre of Geographic Sciences (COGS), Nova Scotia Community College



Chair, Halifax Branch, Canadian Institute of Geomatics

Adjunct professor, Acadia University, Dept. of Earth and Environmental Sciences

Adjunct professor, Dalhousie University, Dept. of Earth Sciences

Bats and Wind Turbines

From MSNBC
by Charles Q Choi

Radar could save bats from wind turbines
Wind turbines inadvertently kill bats and other flying creatures
These images are of the noseleaf of a typical horseshoe bat species (left) vs. that of Bourret's horseshoe bat, the Rhinolophus paradoxolophus (right). Computer modeling indicates the extreme nose is used to create a highly focused sonar beam.
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By Charles Q. Choi

updated 1:40 p.m. ET July 21, 2009
Bats use sonar to navigate and hunt. Many have been killed by wind turbines, however, which their sonar doesn't seem to recognize as a danger. Surprisingly, radar signals could help keep bats away from wind turbines, scientists have now discovered.

Although wind power promises to be a clean source of energy, some researchers have raised concerns that wind turbines inadvertently kill bats and other flying creatures. For instance, in 2004, over the course of six weeks, roughly 1,764 and 2,900 bats were killed at two wind farms in Pennsylvania and West Virginia, respectively. The bats might not be killed by the wind turbine blades directly, but instead by the sudden drop in air pressure the swinging rotors induce, which in turn cause their lungs to over-expand and burst surrounding blood vessels.

"Given the growing number of wind turbines worldwide, this is going to be an increasing problem, no question about that," said researcher Paul Racey, a bat biologist at the University of Aberdeen in Scotland.

Scientists have tried keeping birds from colliding into wind turbines by making their rotors easier to see. And to discourage bats away from wind farms, researchers have tried white noise generators as deterrents. However, these "acoustic scarecrows" have not worked well, Racey said, probably because these sound systems are not strong enough to influence bats within the entire space that rotors sweep through.

A student at the University of Aberdeen first noticed that bats shied away from radar installations while driving past them. He was holding a bat detector out the window to scope out bat activity on the drive back home from out in the field. (Bat detectors are gadgets that scan for ultrasonic bat calls.)

Although bats use sound waves to steer in the dark by echolocation, radar employs radio waves, a form of light, so one might at first assume that radar would have no effect on bats. To see if radar could keep bats away from wind turbines, the scientists at the University of Aberdeen installed small portable marine radar units at 20 bat foraging sites in Scotland — woodland and riverbank areas where insect densities are high. The researchers monitored bat presence for 58 nights using bat detectors.

The researchers discovered that radar helped keep bats away, reducing bat activity by 30 to 40 percent. The radar did not keep insects away, which suggests that however the radar works as a deterrent, it does so by influencing the bats directly and not just their food.

So how does radar keep bats away? The researchers explained that a great deal of research suggests that people can actually hear radar pulses.

"This was noticed when radar arrays first started up during World War II," Racey said. "A portion of radar operators said they heard clicks in their ears when they were switched on."


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Radar signals can lead to small but rapid spikes of heat in the head that generate sound waves, which in turn stimulate the ear.

"A bat's hearing is much more sensitive than ours," Racey noted. "It may be so sensitive that even a tiny amount of sound caused by electromagnetic radiation is enough to drive them out of there."

Future research can design a radar system optimized at deterring bats.