BBC Bitesize - GCSE Physics (Single Science) - Uses and hazards of radiation - Revision 1
Specification. Pearson Edexcel Level 1/Level 2 GCSE (9 - 1) in Geography B ( 1GB0) . You can sign up to receive e-newsletters from Jon to keep up to date with . produce greenhouse gases (carbon dioxide, methane) that. A website to help students of geography learn more about the subject. Advanced level pages being added - look under "Water and Carbon" and of Edexcel content too) GCSE Geography syllabus commencing featuring; Detailed and meticulously follows exam spec, Case studies are up to date and engaging. Archaeology - for the purpose of dating materials and artefacts made from wood. Chemists - Tree rings are the method by which radiocarbon dates are.
Archaeology - for the purpose of dating materials and artefacts made from wood.
When used in conjunction with other methods, tree rings can be used to plot events. Chemists - Tree rings are the method by which radiocarbon dates are calibrated. Climate Science - particularly in the field of palaeoclimatology where we can learn about the environmental conditions of the past, locally or globally, based on what the tree rings are telling us.
By extension, this can also teach us about climate change in the future Dendrology - which also includes forestry management and conservation. Dendrologists are tree scientists and examine all aspects of trees 1.
Tree rings can tell them about the present local climate Though dendrochronology also has uses for art historians, medieval studies graduates, classicists, ancient and historians due to the necessity to date some of the materials that the fields will be handling in their research projects.
Typically, a bachelor's degree in any of the above disciplines are enough to study the data that comes out of dendrochronology. They are the lungs of the world, breathing in carbon dioxide and breathing out the oxygen on which animal life depends. They live in all sorts of conditions too: They are used for decoration in parks and gardens all over the world. They come in all shapes and sizes from the smallest saplings up to the colossal redwoods of North America - it could be said that we take them for granted, yet they are vital to teaching us about many aspects of our past.
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Trees evolved around million years ago 2. Before then, tree ancestors may have looked slightly tree-like but they were not trees in any proper sense. The dawn of the age of true trees came with the evolution of wood in the late Devonian period. Before this, their ancestors would have a recognisable tree form, believed to be that of a giant type of fern that began the process of developing a woody stem.
Wood helps the developing tree to stay strong as it gets older and grows upwards, building new branches and drinking in more sunlight for photosynthesis reproduction. Wood is a solid and strong material as we all know, valued for its longevity and strength. Each season of growth typically annual but not always, we will examine this problem later a new ring is set down in the body of the tree. We can see this in any tree stump, a series of concentric rings circling the heart wood and fanning out towards the edge.
Naturally, the outer rings represent the youngest years of the tree and you may notice that not all rings are uniform - some are thinner, some thicker, some light and some dark.
BBC - GCSE Bitesize: Radioactive dating
These represent growth patterns that reflect the conditions of the season or the year 4 and it is these rings on which the entire study of dendrochronology is based. Dendrochronology is the study of the growth of tree rings and we can learn much from their study. We can date organic archaeological material and create a chronological record against which artefacts can be dated 3. There is much we can learn about the past climate, how freak season-long weather conditions, or periods of climate change have affected tree growth and how it may affect our climate in future.
- Radioactive emissions
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- Dendrochronology: What Tree Rings Tell Us About Past and Present
American Astronomre A E Douglass, who had a strong interest in studying the climate, developed the method around 4. He theorised that tree rings could be used as proxy data to extend climate study back further than had previously been permissible.
He was right, and the more trees that were added to the record, the greater the size of the data could be extrapolated and the more complete picture we could build of our past climate. It was not until the s that archaeologists saw the benefits of the use of tree ring data in their own field 8even though Douglass himself had used his method to date many prehistoric North American artefacts and monuments that had previously not been satisfactorily placed into a definite chronology.
In each growth season, trees create a new ring that reflects the weather conditions of that growth season. On its own, a single record can tell us only a little about the environmental conditions of the time in a specific year of the growth of the tree, and of course the age of the tree at felling, but when we put hundreds and thousands of tree-ring records together, it can tell us a lot more.
Irradiation vs Contamination
Most importantly, assuming there are no gaps in the record and even if there are short gapsit can tell us the precise year that a certain tree ring grew 4. The potential then, even with these two simple sets of data that we may extrapolate from the tree ring data, is enormous. It is an accurate and reliable dating method with a large number of uses in environmental studiesarchaeology and everything in between.
The method has gone from strength to strength and is now a vital method across multiple disciplines. From the s, several seminal studies began at the University of Arizona 67 studying the bristlecone pine of California and hohenheim oak in Germany. Thanks to the work of these studies, we now have an 8, year chronology for the bristlecone pine and in the region of 12, year chronology for the oak. This enormous and comprehensive data set is fundamental to both European and North American studies of the palaeoclimate and prehistory 8.
Dendrochronology Defining Principles 3: Uniformity - that any individual tree ring record may be calibrated against the sum total of the existing record in order that it can be placed in the chronology.
When calibrated, we should be able to tell precisely which year a certain ring was created Limiting factors - that certain weather and climate conditions have an effect on the tree ring growth in any given year or season Aggregation - The strength of the tree ring record is that variations for local conditions are taken into account and any tree ring data set should slot nicely into the existing record Ecological amplitude - Certain tree species will only grow in certain areas.
Ever use a cotton swab to clean your ear, or a band-aid to protect a cut? Well, it may surprise you to know; both of these products were irradiated or exposed to ionizing radiation to sterilize them.
This is simply not the case.
Uses and hazards of radiation
There is a big difference between something being irradiated and something becoming contaminated. When something has been irradiated, by x-rays, gamma rays or electron beams for example, the irradiation stops as soon as the source of ionizing radiation has been removed or terminated. Think of it this way. When you turn a light on, the room is filled with electromagnetic radiation in the form of visible light. The instant you turn the light off, the electromagnetic radiation is gone.
The same can be said about the energy of ionizing radiation.
However, even though the irradiation stops, the biological effects may still occur if unrepaired cell damage has been inflicted. Contamination is much different.
When contamination has occurred, the source of the ionizing radiation itself is transferred, such as when radioactive isotopes in solid, liquid or gaseous forms are introduced into the environment. For example strontium, a radioactive isotope found in spent reactor fuel which can cause a variety of bone disorders including cancer, can become airborne and settle on buildings, trees and grass, thus contaminating them.