Geology question

[Hans Deventer]

Madeira is a volcanic island, that is, is was formed by volcanic eruptions but there is no longer an active volcano there.

Now the piece of rock on the picture puzzled me. I understand horizontal layers and vertical layers, but I don't understand how they can be in this piece of rock at the same time, actually crossing each other! The vertical layers looked like basalt.

Can anyone explain?

[Billy Cox]

My uneducated guess would be that the vertical layers are the result of deep fissures being filled in with newer rock.

[Joel Merrill]

My uneducated guess would be that the vertical layers are the result of deep fissures being filled in with newer rock.
That could be. I'm not an expert either but it could be that the surrounding rock wasn't rock yet and those are volcanic lava vents from the eruption.

Joel

[Billy Cox]

That could be. I'm not an expert either but it could be that the surrounding rock wasn't rock yet and those are volcanic lava vents from the eruption.

Joel

Or maybe when God was creating all the fossils, he created that too. :basic03

[Anne and Dwayne Hood]

Maybe the horizonal layers hardened over the years of eruptions, then the vertical layers of lava ran down over the other layers, thus forming vertical layers that later hardened--all happening during the years that the volcano was active. I studied geology and other "ologies" in college, but not about the volcanoes. This is my reasoning.

[Ryan Scott]

I'm not any more an expert than anyone else, but I'd say the vertical lines are either actual lava or really hot steam venting from the volcano.

[Jim Franklin]

As a Physical Geography student I would surmise that the force of the volcanic eruption caused fissures in the caldera (the walls of the crater) as others have suggested and feel that I can affirm their responses.