Rocks from the heavens
Our solar system is not only made up of the sun and planets. A lot of stone and ice blocks also rotate around the sun. Some are as small as dust grains, while others are several km wide, as big as a city. Comets are largely made of ice and stone and asteroids of stone and metal. Most asteroids can be found in the so-called asteroid belt, a ring of small and big rocks between the planets Mars and Jupiter. Most meteorite impacts can be traced back to rocks that came from this asteroid belt. A meteoroid usually is a small piece of a comet or asteroid. When the meteoroid travels through our atmosphere, it starts to burn and leave a bright trail of light in the sky, called a meteor or a falling or shooting star. Leftovers of this meteoroid, which fall on the ground, are called meteorites.
Meteoroids regularly hit other things in space. Just take a look at our moon. You can see that it's full of craters with binoculars, which are "scars" from previous collisons. But it is much more difficult to find impact craters on Earth. Up till now, there are less than 200 proven impact crater found. Geological processes continuously change the surface of the Earth and the evidence of previous impacts is often destroyed or hidden. Most meteoroids that cross Earth's orbit are small and burn up in our atmosphere. But once in a while, a big meteoroid travels close to Earth, which can crash and create an impact crater.
Around the earth in 500 million years
One finds a steep cliff east in the crater, which consists of dark shale. This shale tells us the history of what happened after the crater was formed. In this shale one can find fossils of marine creatures like crustaceans and extinct creatures called trilobites. Trilobyte fossils can be found across the globe and we know that they can be lived 250-500 million years ago in a tropical ocean environment during a geological period called the Paleozoic. So that means that Ritland must once have been a tropical sea!
The continents move across the surface of the Earth with a speed of 1-10 cm per year. When we go back in time, we can see that Norway moved from the South to the North of our planet and that Norway did have a tropical climate in the period after the impact. So the local fossil evidence from the Ritland Crater fits the geological history of Earth.
Read more about the geological history of Norway here.
Visit the virtual fossil museum here.