How do geologists differentiate between geologic events that took place over thousands of years and those that happened very suddenly or very quickly?

Question

I’m interested in reading about sudden or rapid geologic events, like earthquakes, volcanic activity, and so forth, but haven’t heard a satisfying explanation of this, i.e. whatever I read didn’t stick with me. If someone can give me a basic enough explanation, that would help as I look for stuff like this.

Thanks!

In: Earth Science

Answer 1

In most geologic time, 1,000 years is almost instantaneous.

There is a thing called the KT boundary the boundary between the Cretaceous and Tertiary periods (~~Kreide-Trias~~ Kreide-Tertiär which has now had a namechange to the more precise Kreide-Paläogen in German and it’s now the KP boundary) where in the Geologic record there is a thin layer of clay in the boundary between these periods. This layer of clay is high in Iridium all over the world and strongest in Mexico. Iridium is an element that is rare on earth, but prevalent in meterorites. The conclusion then is that one day a massive meteorite landed on earth and the explosiong sent parts of the meteorite all over the earth (probably similar to how an atom bomb exploded in the air puts trace levels of radioactive contaminants all over the earth.

If we accept the explanation of the meteorite spreading iridium all over the earth and the change from reptile to mammalian then we can conclude that this point in Geological time is precisely known.

ETA /u/GiantClaw points out that KT is Kreide-Tertiär (which was name changed to Kreide-Paläogen) not Kreide-Trias.