Rock of ages

I did like this rock, all mossed up, sitting proud and immovable in the middle of a wide stream in the South Lakes. I was there yesterday drawing and liked this big boulder. I wonder how it got there; maybe by melting glaciers?
It must stay unmoved, despite the shape or strength the stream. So much thick moss has grown on it, years and years worth, it just doesn't move, despite all the activity of changing seasons, rising levels of rushing water, violence of sudden flooding or the glass calm and tinkling of a hot summer's day; the boulder remains implacable .
I also like the stacking of the different tones and textures; it's a little like three different images.