‘Floating’ quotations can disrupt the flow of an essay. They are rarely used in scientific publications and should be avoided. Indeed, it is generally best to avoid quotations unless you absolutely cannot phrase the concept in your own words. Lengthy quotations are a) difficult to reproduce under examination conditions; b) disruptive to the flow of an essay and c) lead to a ‘cut-and-paste’ feel. Similarly, please don’t use footnotes as they break the flow of your argument. If the data isn’t important/relevant enough to include in the main body of the text then exclude it entirely.
Lengthy, relatively bland quotations such as the following give essays a cut-and-paste feel, even when the material is relevant:
Large sediment yields are associated with rivers that drain active orogenic belts (again on a large scale) and sizeable regions provide more sediment per unit area due to the sheer amount available. “Sediment yield increases with mean annual runoff but there can be differences in the rate of increase, depending on the amount of vegetation around. With less vegetation, runoff penetrates the soil more and so there is a progressive increase at the rate in which sediment yield varies.” (Knighton, 1998)
Note that quotations also require a page reference in the citation.
Quotation marks are generally unnecessary for simple statements of fact, for example:
The Tree Observatory “used rings from some 300 sites across Asia to measure the effects of 54 eruptions going back about 800 years.”
The use of quotation marks here is totally unnecessary (a citation is also required). The same applies for the following:
Volcanic emissions are likely to have remained constant in their composition over time, containing “water, carbon dioxide, sulphur, halogens and many other species in small amounts (e.g. nitrogen, argon, trace metals and perhaps methane)” (Martí & Ernst 2005).
This sentence includes a citation, but no page reference.
It is generally better to express concepts in your own words, rather than stitching together quotations (especially if the quotations ‘float’ in the text). For example:
Pete Francis explains the mechanism for sulphur dioxide being converted into sulphuric acid in the stratosphere:
“Sulphur dioxide reacts with hydroxyl radicals formed by photo-dissociation of water vapour in the upper atmosphere. Via chemical routes not fully understood at present, tiny droplets of sulphuric acid are formed” (1993, page 371).
Could have been:
Photo-chemical processes in the stratosphere convert sulphur dioxide gas to an aerosol composed of tiny droplets of sulphuric acid (Francis, 1993)