It varies depending on the environment where it fossils and the type of organism:
1-Conservation of organs without modification or with discrete modifications (recrystallization). Is the usual case of hard parts (shells, bones, teeth, calcareous algae ...), and exceptionally soft parts in very particular conditions: ahem. mammoths conserved in icy soils of siberia or in hydrocarbons (ozokerites) north of the Carpathians, insects included in fossil resins (baltic amber).
2-Conservation of organs after their replacement by a different subject preserbando its structure with more or less detail. (It is a process called metasomatism) ahem. silicification of trunks of trees, vertebrate bones or the pyritization of ammonites.
3-Conservation in the form of mold of the organism, internal or external to it. It is often the case of ammonites, shells or conches.
The fossilization process is said to start at 100ºC and pressures above 1Kb (kilobar). Conyeva an exchange of atoms, between the original organism and the matter that surrounds it. They are called fossiligenetic processes. Some of the processes are: carbonation, silicification, phosphatization, pyritization, dissolution.
1954- Brown v. Board of Education
1955- Emmet Till murder
1956- Montgomery Bus boycott
1957- Civil Rights Act of 1957
Highlander Folk school 25th Anniversary
I don’t know the rest sorry
In two words - Civil War.
Having the Mexican Cession to divide up between slave states and free states aggravated the bickering that had been going on for at least 30 years between North and South - - though
the slavery issue was a thorn in the American side at the Constitutional convention in 1787 as well.
Just had a history grad school course on the American Civil War, and the general consensus from the reading was that the Mexican Cession was one of the final straws that led to the break up of the Union in 1860-61. The repercussions of the Civil War are still being felt today - though it is diminishing finally.
What are 5 influences Mexico has made on the United States? - - - California, New Mexico, Arizona, Nevada, Utah, and one extra - - Colorado.
Cultural contributions are many - especially in the states mentioned above. Most common nationwide - Mexican retaurants - - the cuisine.
A purple stone traded by ancient merchants in eastern Oklahoma was the obsidian.
In ancient times, pre-Columbian civilizations like the Mayans used obsidian for many purposes, including to make tools and weapons (arrowheads, blades, etc.), as well as ritual and ceremonial objects (for burials for example).
There is believed to have been obsidian trade routes all throughout the American continent, even though obsidian does not itself originate in Oklahoma.
