Ancient Seas May Predict Future Environments
Trees Provide Chemical Clues to Ancient Environments
Evaporation Held Ancient, Giant Lake In Check
As North America emerged from under a continental glacier at the end of the last ice age, a gigantic lake formed in Canada. Fed by the melting glacier, Lake Agassiz grew to cover all of what is now Manitoba and a good portion of Ontario. UC geology professor Thomas Lowell has investigated a long-standing mystery involving this lake – a significant drop in water level known as the Moorhead Low. It has long been believed that the Low was created when a new drainage pathway opened. Lowell’s research shows that, although water levels did drop, the surface area of the lake increased more than seven-fold. He thinks the lower water levels were caused by evaporation. While the melting glacier produced a lot of water, Lowell notes that the Moorhead Low was roughly contemporaneous with a chilly, dry period known as the Younger Dryas, when the dry air would reduce rainfall and promote evaporation of liquid water and sublimation from ice cover. For more on this topic, follow this link.
Did Southern Factors Affect Northern Glacial Retreat?
|Thomas V. Lowell|
Why Didn’t a Cold Snap Encourage Glaciers?
As the North American glacier retreated at the end of the last ice age, there were occasional periods of very cold climate. One cold dry period around 12,000 years ago is known as the Younger Dryas (a tundra plant of the genus Dryas flourished then). UC geology professor Thomas Lowell has investigated the Two Creeks buried forest in Wisconsin to gain some understanding of the impact of this thousand-year-long cold snap. It appears that the continental ice sheet did not charge forward although the climate was cooling. Lowell thinks it is possible that sunlight may have been holding the icecap back at that time.
In Mass Extinctions, Different Environments Fare Differently
|Arnold I. Miller|
High-Resolution Records of Himalayan Glaciers Emerge
|Lewis A. Owen|
Tropical Watersheds May Reduce CO2 – Or Increase It
What Affects Levels Of Vanadium and Strontium In Your Drinking Water?
The presence of vanadium in drinking water is a growing concern, and vanadium contamination may soon be regulated. Tammie Gerke, research associate in geology, has tracked vanadium minerals in corroded iron pipes used to transport drinking water. Most of the vanadium was found in the form of vanadinite, a mineral also containing lead. It is likely that deposits of vanadium-containing minerals originate in lead pipe farther up the distribution system. Gerke’s work suggests that small disturbances caused by flowing water or chemical reactions in the water, can greatly elevate vanadium levels. Gerke’s research characterizes the different compounds containing vanadium found in iron pipes. Similarly, there was little concern until recently about the presence of non-radioactive strontium in drinking water. As evidence for health effects grows, the US Environmental Protection Agency is considering regulations. Gerke and colleagues have examined how strontium accumulates in iron pipes used to carry drinking water. More importantly, they looked at how strontium absorbed into the corroded inner surfaces of iron pipes is released. Under certain circumstances, they found, it is possible to release excessive quantities of strontium, both as ions and as components of corrosion particles.
The Devonian Period (416 million to 359 million years ago) concluded with a major extinction, but the biological crisis began in the Middle Devonian. A record of this initial biocrisis is found in the rocks of the northern Appalachian Basin. That’s where James Zambito, recent UC geology PhD recipient, tracked evidence of events throughout the crisis. The crisis began with the invasion of tropical animals replacing existing species. The invaders died out as the former animals returned. Finally, the recurrent “native” fauna, too, died out. At each stage, Zambito has identified environmental changes to support each transition in animal life, including global warming. To uncover these connections, he employed a multi-disciplinary approach that may be useful in other regions.
Molluscs On the Move
Conventional wisdom, as codified in a hypothesis known as Tropical Niche Conservatism, states that larger taxonomic groups (such as genus, family and order) originate at a particular global latitude and pretty much remain at that latitude until they become extinct. UC geology doctoral candidate Andrew Zaffos analyzed the extensive records of the international Paleobiology Database and finds that life is not as conservative as hypothesized – at least for clams and snails of the Cenozoic Era. Zaffos believes a number of factors may contribute to the evidence he found for substantial changes in preferred latitude over tens of millions of years.
Ancient Plants Provide Insight
Some early plant fossils – from Devonian and early Carboniferous time (410 million to 320 million years ago) – are yielding insights into ancient environments. UC doctoral candidate in geology Zhenzhu Wan has looked into the relationship among environmental factors, water-use efficiency and isotopic composition of these ancient plants. Eight fossil plant types display variations that can be attributed to water use efficiency and genetic variation. Some of the plants are preserved in the same locations, which will allow research within the same environment. Some of the plant types have a long history in the fossil record, which may provide ecological information from different habitats over long periods of time.
Miniature Fossil Reefs
The New Point Stone Company quarry near Napoleon, Indiana, is famous for its fossils, particularly echinoderms – a phylum of marine animals including starfish and sea urchins, but also stalked animals such as crinoids and cystoids. James Thomka, a UC graduate student in geology, has studied the rocks exposed at this quarry and has found an intriguing glimpse into an ancient environment. The Osgood Formation rocks exposed at the quarry are Silurian in age, more than 400 million years old. Thomka has found a series of miniature ancient reefs forming an undulating record of the Silurian sea floor. Scattered about this surface are remnants of echinoderm stalks. These attachment structures are not randomly distributed. It is clear that different species found different parts of the reefs more hospitable.
Tracking Layers of Rock
Geologists have known about a layer of rock in eastern Kentucky known as the Waco Member for a century, but it has not been easy to determine how this layer fits into the sequence of Kentucky’s geology because its rocks have been chemically modified and bear few specimens of useable fossils. Nicholas Sullivan, graduate student in geology at UC, took a fresh look at the Waco Member using magnetic measurements and traces of fossilized burrows to define a stratigraphic pattern. This pattern seems to represent an episode of rapid flooding, possibly caused by a global rise in sea level. If so, the pattern can serve to connect the Waco layers to other geologic deposits in the region.
Evidence of Glacial Cycles
The last Ice Age was not a single event, but a series of advances and retreats over many years. Scientists are still sorting out these cycles. Gianna Evans, UC graduate student in geology, and colleagues compared the sequence of annually deposited sediments in Reid Lake, Ontario, to other glacial deposits and found a consistent sequence of events. Evans specifically tracked material carried out into the lake by icebergs. This “ice rafted debris” appears in cycles of different length depending on whether glacial ice was melting or advancing.
Canal Sediments Yield Information
Our knowledge of geology was greatly expanded during the great canal-building age of the late 1700s and early 1800s, when canal-builders exposed patterns of subterranean strata for the first time. Now, the canals themselves can offer clues to environmental changes. UC geology student Nicholas Bose and colleagues explored the abandoned Miami and Erie Canal that once linked the Ohio Valley to the Great Lakes. The canal was regulated by a series of reservoirs. Once the canal was abandoned, the reservoirs filled up with a sedimentary record of climate change over the past century. Rose found concentrations of metals related to industrial activity, but also patterns of layered deposits that suggest short-term cycles of climate change.
Sorting Spain’s Puzzle
The mountains of northeastern Spain are a sort of jigsaw puzzle assembled of pieces of continents colliding over millions of years. Julia Linnaea Wise, whose primary interests include tectonics and petrology is looking at this area as part of a larger study of the ancient supercontinent, Pangea. She has found several types of garnet that occur in specific types of rock. The chemical composition of these different garnets provides clues to the tectonic forces at work in the region.
When volcanoes erupt, they project more than lava. Liquid streams of mud and ash flow down the volcano. These flows harden into masses of sediment called lahars. UC geology graduate student Julia Linnaea Wise and colleagues studied lahars produced by volcanoes located in the Cascade Range of Oregon. Although all the volcanoes were in the same tectonic setting, and the lahars associated with them appear similar, there are strong differences in amounts of trace elements. Lahars associated with the same volcano have similar trace element chemistries.
How Mountains Are Carved
It is hypothesized that, as geologic forces push mountains upward, a glacial “buzzsaw” grinds the peaks down. UC geology graduate student Scott Reynhout has charted evidence of this buzzsaw mechanism in the Ladakh Range on northwestern India. Bedrock weathering rates increase rapidly with altitude, Reynhout found, with erosion caused by glacial mechanisms working selectively to destroy high topography. Conversely, hillslopes at lower elevations may have seen little change for up to 5 million years.
Dating Himalayan Glaciers
Scientists are still sorting out the timing and extent of ice-age glaciers in easily accessible locations like Europe and North America. Imagine the challenges in a remote region with active glaciers like the Himalaya region of Asia. The area has strong climate variation, from near-deserts to monsoon-drenched valleys, further complicating the work. UC geology graduate student Todd Longbottom has taken a significant step toward unraveling the land-forming effects of glaciers in Northern India by determining how long different surfaces were exposed to cosmic radiation and measuring physical features.
Erosion or Tectonics?
As erosion scours the surface of the planet, it exposes fresh surfaces of rock. These new surfaces are exposed to cosmic radiation which creates tell-tale variations of common elements. The longer the surface is undisturbed, the greater the concentration of these “terrestrial cosmogenic nuclides.” Kathryn Hedrick, graduate student in UC’s geology department, studied concentrations of one such nuclide, an isotope of beryllium, in two Himalayan valleys as part of an effort to understand how erosion operates on bedrock there. Preliminary results suggest that tectonic uplift contributes more to erosion than glacial processes.
Understanding Slippery Slopes
The Cincinnati area is afflicted with a very high number of landslides. Much of the blame can be directed at a particular layer of bedrock known as the Kope Formation. This formation is distinguished by thin layers of limestone separated by thick layers of mudstone that – when soaked with rain or groundwater – turn into mud. Nadeesha Koralegedara, UC geology graduate student, conducted a detailed analysis of Cincinnati’s Kope mudstones and determined that there are two distinct types. A laminated type has less moisture and greater durability than a non-laminated type. Because both types exist throughout the Cincinnati area, geotechnical analysts should take to distinguish which type of mudstone is most common in a particular area.
Carbon Storage In Mountainous Regions
The amount of organic carbon affects soil fertility, agricultural production and levels of greenhouse gases like carbon dioxide in the atmosphere. Storage of organic carbon in soil is dependent on climate, with humid subtropical areas showing higher content than drier regions. In the Himalayas, there is a wide variation in precipitation. Longbottom expects to find a similar variation in carbon storage, with higher concentrations of soil organic carbon in the wetter areas.
Carbon Storage In Cities
It is known that living things can pull carbon from the air, potentially moderating levels of carbon dioxide generated by human activity. It is not known how effective green spaces and forests located within cities are at absorbing carbon dioxide. UC geology student Lily Soderlund gathered soil samples from Cincinnati’s Burnet Woods, from a managed (irrigated and fertilized) urban lawn and from an unmanaged urban lawn. Her analysis shows variation in carbon stocks between managed soils and unmanaged soils and helps establish the potential of urban spaces for meeting greenhouse gas reduction goals.
A New Type of Clam?
The various species of the genus Chione, one of the so-called “Venus clams,” are found throughout the Caribbean region as both recent and fossilized specimens. Recently, specialists split a common species of Chione into two species with different geographic distributions. UC geology graduate student Sarah Kolbe has now found a third, distinct type of Chione from the southeastern Bahamas. Further, her measurements of specimens from 72 localities indicate that her new type is more distinct than the two previously accepted species. The work raises some intriguing questions regarding the nature of biogeographic boundaries in the region.
Iron Minerals in Drinking Water Pipes
Cast iron pipes used to distribute drinking water eventually develop corrosion scales made up of various iron oxides. These oxides are found naturally as minerals, which include lepidocrocite, magnetite and goethite. Matthew L. Jones, a graduate student in UC’s geology department, looked into the origin and formation of the magnetite found in pipes from a drinking water distribution system. Unlike the majority of magnetite found in lava from volcanoes, the magnetite found in corrosion scales is formed at low temperature. Other low-temperature magnetite is formed by bacteria, and it is likely that the magnetite found in pipe has a bacterial origin as well.
Global warming and Coral Larvae
Reef-building corals are tiny animals that have a two-phase life cycle. From a mobile larval stage they settle to become a stationary adult. Because an adult coral can never move, it is important for coral larvae to be able to travel widely so coral communities can intermingle and maintain genetic diversity within a species. UC geology student Sharmila Giri studied the larval energy reserves of one species of coral as an undergraduate at The Pennsylvania State University. She looked, in particular, at how this energy supply is affected by increasing temperature, and showed that it is depleted faster at higher water temperatures. As global climate changes, sea surface temperature rises above the heat tolerance of many species of corals, usually in the summer months when larvae are abundant. This means an increase in sea surface temperature may potentially affect the dispersal range of coral larvae, and possibly lead to greater post-settlement mortality and population fragmentation.
Wet Streams In A Dry Land
Southern California is a relatively dry place, with a lot of people who need a lot of water. An analysis of decades of fresh-water runoff by UC geology student Katherine Finan suggests that the more urbanized the region becomes the more fresh water runs out to sea. Finan found that some streams which once totally dried up in late summer now run year-round. It’s likely this extra run-off is caused by over-watering lawns and gardens.
Human Effects on Sea Life
It’s accepted that humans significantly change the environment, but how do these changes affect the clams and snails living nearby? In order to answer this question, UC geology graduate student Kelsey Feser looked at seashell deposits around St. Croix, US Virgin Islands, which were covered by dense beds of seagrass. By doing so, she was able to track how deposits of seashells occur naturally compared to areas with significant human development. Her initial results – particularly when compared to samples collected 20 and 30 years earlier - illustrate how different types of human activities affect communities of sea life.