several questions about geology ! HELP !!!!?

Question

1) Under what conditions does a glacier retreat ?
2) Which one happened first ? Pangaea or Hard Parts ?
3) What does unconformity indicate about the geologic history in an area ?
4) Which organism have the best chance of being preserved as fossils ?

please help me, i am confused about these questions...

Answer 1

1) Glaciers retreat when the temperature increases, causing the glacier to melt.
2) The oldest fossil with hard parts is about 550 million years old, while Pangaea existed about 250 million years ago, so hard parts in organisms appeared first.
3) An unconformity indicates a break in the sedimentary geologic history of the area.
4) A wide variety of factors influence the chances of an organism being preserved, but here are a few important examples...
-In general, large organisms have a better chance of fossilization than small ones. (For example, there are more dinosaur fossils than insect fossils.)
-The hardness of the body parts of the organism. (For example, a sea star is more likely to be fossilized than a sea jelly.)
-Certain environments favor fossilization more than other. For example, an animal that dies in the mud is more likely to be preserved than one that dies on a dry surface.

Answer 2

1) Glaciers will retreat if there is a rise in temperature or a decrease in the amount of precipitation. Usually this is resulting from some sort of climate change, but other (minor) factors may play a role in increasing temperature or reducing precipitation (snow mainly). A glacier will retreat if accumulation of new snow and ice is less than the amount of water being melted or evaporated. This is more likely to happen in glaciers at lower elevations as they generally experience higher temperatures.

2) Hard parts in organisms came about during the Cambrian Explosion, about 530 Ma. Pangea existed about 250 Ma (million years ago).

3) Basic answer: unconformities represent time gaps in the rock record.
Depending on the type of unconformity, you can determine what happened to form the unconformity
Ex: Angular unconformity - where flat lying sediments lie on top of rocks which were not horizontal. Erosion will have taken place.
Search on google for unconformity. Wikipedia`s description isn`t too bad

4) Organisms with hard parts, that can be burried in sediments that will preserve them.

Answer 3

1) Glaciers are ice. What can cause a big piece of ice to melt?

2) What on Earth is Hard Parts? What do they teach you kids?

3) There are three types of unconformities. Look them up. They all involve erosion or rock. Rock represents time. What happens when rock erodes?

4) Not squishy ones.