geology help, salt water vs. fresh water?
Question by : geology help, salt water vs. fresh water?
1. Why are icebergs a serious potential hazard to ships?
2. Why is it easier for a person to float in the Great Salt Lake or the Dead Sea rather
than in a freshwater lake? Would a ship float higher on the Great Lake or the ocean?
3. If an object floating on a lake is 25% submerged, what is the density of the object?
4.Why are the concentrations of metals higher in freshwater than seawater?
5.Why is seawater referred to as “salty?” What’s the difference between fresh and
seawater?
6. Given what you know about density differences, what happens to the salinity
concentration from the sea landwards at a delta? Do the waters mix, or tend to
stay separate?
7. What is happening to the salinity concentration in an estuary where the salinity
actually increases from the sea towards the river as it does at Spencer Gulf in
Australia?
8. Why is saltwater encroachment an issue with coastline water wells? Do density
differences keep them separate?
Best answer:
Answer by Chris
DYOH!
Know better? Leave your own answer in the comments!
Reader Comments
Hmm… you know, it’s true, you really should do your own homework. Most of these are absurdly easy.
(1) Icebergs are hazards because 90% of them is beneath the water, it’s very wide beneath the water, and it’s almost as strong as steel — so if your ship runs into an iceberg and your hull isn’t thick enough or strong enough, you’ll get a tear in your hull, as per the ill-fated RMS Titanic.
(2) The salinity in the Great Salt Lake and Dead Sea are significantly higher (the Dead Sea is 8x higher than the ocean average). This makes it more dense. The more dense the liquid you want to float in, the higher you’ll float (see buoyancy). Take it to an absurd level… you start with very fluid Portland cement, you’ll sink, versus dense cured concrete, which you can walk on.
(3) I don’t know. Ask one of the guys in the Physics section.
(4) Um… it really isn’t true. But, in surface waters, the masses involved are often relatively small and the chemistry of the water can be strongly influenced by the chemistry of the rocks in the area. On the other hand, the ocean are huge relative the local input of water carrying whatever amount or type of dissolved solids. So the ocean is buffered, and any source of metals is swamped by dilution of the entire freaking ocean.
(5) Salt water contains salts such as sodium chloride, which is NaCl, which is known as common table salt. Freshwater may contain salts as well, but in very low concentrations, making it “fresh.” You really had to ask this one?
(6) Deltas remain much more separated as far as salinity goes than a non-deltaed river, because of the way that the rivulets and tributaries wind through the sediments and slam into the ocean. However, it isn’t perfect, and salinity does mix somewhat as you go from the “beginning” of the delta (so on the river’s end) to the ocean-side of the delta.
(7) Areas such as Spencer Gulf are uniquely enclosed and lose more fluid to evaporation than normal, which allows saline water to flow “upstream” and increase salinity in a reverse circulation compared to a normal estuary.
(8) Yes, density keeps them separate when things are in harmony to a degree. Saltwater is denser than freshwater (about 1,200 kg/m^3 compared to 1,000 kg/m^3). Primarily, however it is the continuous outflow of freshwater that keeps “pushing back” on the saltwater. But if you suck too much water out of a coastal aquifer, the saltwater will become “more powerful” and push the freshwater back, and then intrude the coastal aquifer. This is bad, because people cannot drink seawater, and once it’s in the aquifer — there is nothing that can be done, not even by Mother Nature, to get it out. So you’ve eliminated your water source.
I hope this has helped. But next time, at least try to answer some of them and let me know what you already know, okay?