Fosseis.

-Fosseis-

 

Os Fósseis (do latim fossilis, tirado da terra) são os restos ou vestígios que são preservados de animais, plantas ou outros seres vivos em rochas,

com por exemplo moldes do corpo ou partes deste, rastros e pegadas.

Eles são objectos geológicos com uma origem biológica mais ou menos remota. É fundamental ter bem presente que eles não são organismos.

Muitos fósseis, por exemplo os fósseis de pegadas ou de galerias, não são orgânicos, e nunca foram organismos.

Desde incio, o Homem observa e tenta interpretar a natureza. Desde muito cedo nós encontramos rochas com impressões em forma de conchas, ossos de animais e folhas de plantas, que obviamente são os fósseis. 

Os fosseis encotra-se em rochas sedimentares.

Esse material é de grande importância para a Ciencia, pois prova a existência de organismos que viveram antes de nós dando-nos pistas de como era nosso planeta antigamente.

Existem dois principais tipos de fósseis: os somatofósseis e os icnofósseis.

Somatofósseis:

Os restos orgânicos de fósseis que foram preservados. É uma marca importante para registrar o passado biológico e geológico de nosso planeta, assim aprendemos mais e mais sobre nossos pasts dos planetas e que tipo de criaturas viveu aqui antes de nós.

Icnofósseis:

Os vestígios fósseis,com por exemplo; pegadas ou as marcas de folhas, galhos, entre outros, que indicam a existência de seres vivos que viveu no passado. São também meios importantes e muito úteis para medir todas as diferentes fases da evolução dos seres vivos ao longo das diferentes eras geológicas.

Fossilizão-

O processo natural de formação de um fóssil é denominado fossilização.

Fossilização é um processo pelo qual pequenas partes de substâncias orgânicas ou inorgânicas passando formando uma transformação, 

quando submetidos a condições ambientais especiais de temperatura, pressão, o resultado é a mineralização da substância, que é como os cientistas podem coletar informações sobre a vida do fóssil tinha antes de falecer, por exemplo;

-Quando aquele ser morreu.

-Em que época ele viveu. 

-Qual a sua alimentação. 

A fossilização é um processo extremamente lento e complicado, que dura até milhares de anos.

É também um mecanismo raro, uma vez que, para que ele possa ocorrer, as condições precisam ser extremamente favoráveis para o organismo funcionar.

Existem vários tipos de fossilizacão;

1-Incrustação 

2-Mineralização  

3-Carbonização/Incarbonização 

4-Mumificação 

5-Moldagem 

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Geologic time.

-GEOLOGIC TIME-     Before i show you the geologic scale, I just thought I would throw in some information; The geologic scale displays all of the different bits and chunks off time that has been since the earth first became the earth. In these scales you can see eons, eras, periods, epochs and ages. The ones who first thought we should have one of these scales were the miners 1500s and the 1600s. they wanted, and needed, to understand geological relationships of different rock units were miners. Mining had been of commercial interest since at least the days of the Romans. Nicolaus Steno, in 1669. noted the relationships of the different rock units as he described two basic geologic principles. The first one said that sedimentary rocks are laid in a horizontal manner And the second one said that the younger rocks were deposited on the older ones. If this is "complicated" to understand imagine this; You are painting a wall, the older layers were put on first, hence, it will find itself at the bottom, while the newest layer finds itself on the top. And then in 1795, James Hutton added an additional concept which was then later emphasized by Charles Lyell sometime in the early 1800s. This basically says that the natural geologic processes uniform  in frequency and magnitude throughout the time that passes. This idea is known as the "principle of uniformitarianism"

                               - The formation of The Sun, Earth and Moon -                                

So, a very long time ago (about 5 billion years) in a perfectly normal and ordinary place in the galaxy, a supernova exploded, pushing a lot of its heavy wreckage into a nearby cloud of hydrogen gas and interstellar dust. 

The mixture grew hot and compressed under its own gravity, and at its center a new star began to form. Around it swirled a disk of the same material, which grew white-hot from the power of the great forces. That new star became what is now our Sun, and the glowing disk gave rise to Earth and other planets close by. We can see things just like this happening other places in the universe. While the Sun's size and energy grew, beginning to ignite its nuclear fires, the hot disk slowly got colder. This action was extremely slow, lasting millions of years. 

At some point during this time, the Sun ignited. Even though the Sun was not as bright as it is today, the process of ignition had the energy it needed to blow away most of the gaseous part of its surface.The chunks and other stuff that was left behind continued to collect into a handful of large, stable bodies, sort of like planets. Earth  was the result of the third one of these. We know that the process of accumulation was violent and spectacular, because the smaller pieces left huge visible marks marks on the larger ones. This happened about 4,6 billion years ago.

It took another hundred million years before what is now our moon appeared. There are 3 main theories as to how our moon could have gotten created, so we can not really be sure.

The first one of these theories (Giant impact hypothesis) is that a mars-sized body (given the name Theia) collided with Earth, throwing chunks and bits from Earth (which was a young planet at the time). Gravity then kind of glued these particles together, creating what is know as our moon. This sort of formation would explain why the moon is made up mainly by lighter elements, making it less dense than Earth. 

The second theory (Co-formation theory) explains that moons can also form at the same time as their parent planet. With this theory, gravity would have caused material in the early solar system to draw together at the same time as gravity bound particles together to form Earth. Such a moon would have a very similar composition to the planet, and would explain the moon's location as to where is it today. But this theory doesn't sound right because the moon is less dense than earth, which likely wouldn't happen if they were made at the same time with the same elements.

And,  the third and last theory (the capture theory) says that perhaps Earth's gravity bumped into a body that was just passing by. This has also happened with other moons in the solar system. Under the capture theory, a rocky body formed elsewhere in the solar system could have been drawn into orbit around the Earth. The capture theory would explain the differences in the composition of the Earth and the moon. However, such orbiters are often oddly shaped, and do not have the circle-like shaped body like the moon, so this theory doesn't really make the sense it should make.

Personally, I think theory number one - the Giant impact hypothesis - sounds the most accurate, but you can decide whichever one you believe in!

-Gabriela