Petra, I know more about the geology of the northern islands, but know a bit about Catalina, and know quite a bit about California Tectonics. I paste the text in below and make comments between the "**"s

Geology of Catalina
Catalina was not formed like the other Channel Islands. **not clear what this means, but as far as its uplift, it is very much like the other islands. Having volcanic rocks is common to many of the other islands. And, the metamorphic rocks that are exposed on Catalina are at depth beneath some or all of the other islands**

Catalina is the result of a collision between two plates. The Northern Plate was moving from Mainland towards the sea.
**What northern plate? Did they mean North American plate? And, with respect to what?

The Pacific Plate was moving from the sea towards Mainland. **The Pacific plate was moving away, not towards, the North American plate when the subduction was occuring-it has been moving towards the northwest most recently, not towards the east.**

As a result the two plates collided. This happened millions of years ago.
**I still don't know what the Northern plate is. The edge of the Pacific plate came closer to North American plate because it was growing along the East Pacific Rise-material is added onto the west side of the Pacific plate as it moves to the northwest. The North American plate is moving west (relative to the hotspots in the deeper mantle) and partly overtook the retreating edge of the Pacific plate....**

The North American Plate had another collision with a smaller plate. The plate Farralone slipped under the North American plate for thousands of years. **Try tens of millions of years-the Farallon plate and its microplate descendents subducted beneath the North America plate as it spread away from the Pacific plate...**

When this happened the plate became metamorphosis rock.
**the word is metamorphic. The subducted crust and the sediment above that went along for the ride was metamorphosed**

Then as the two upper plates collided,
**Which 2 upper plates?**

and slid along each other, stretching and pulling the earth's crust (just as it does at the San Andreas Fault),
**Did they collide, or run parallel to each other? How can you collide and stretch at the same time. This just does not make any sense**

a rupture occurred and the schist from the lower Farralone Plate erupted up with volcanic rock and ash to become Catalina Island.
**OK, I have been working on these models. This is not what happened. I'm a co-author on a paper, and my thesis was on, a model that spreading between the Pacific plate and a microplate descendent of the Farallon plate ceased about 19 million years ago. The microplate was partially subducted and present in the lower crust before then. When spreading ceased, it became part of the Pacific plate, which was moving away from North America. The upper crust, now part of the Transverse Ranges, went along for the ride, stripping off the lower crust where Catalina Island would one day be. Volcanism occurred after this stretching was well underway. Then, in the last few million years NW-SE right-lateral fault became active in the area. A bend in one caused convergence in the area of Catalina Island, and up it popped and is still popping......
Chris