1 Iceland: What we know and what we don’t Gillian R. Foulger Durham University, U.K. Rift to Ridge ‘07 meeting, June 2007 National Oceanography Centre, Southampton Invited keynote talk

2 What we know and what we don’t is person-dependent

3 Is Iceland hot?  T = 93˚C (Ribe et al., 1995)  T = 0-200˚C (Foulger et al., 2000)  T = ˚C (Herzberg et al., 2007)  T = 270˚C (Langmuir et al., 1992)

4 Is the Iceland “hotspot” a spot? Centre of “the” Iceland plume

5 “How does a hotspot influence the development of an oceanic basin…” How does breaking the law affect crime?

6 Other plume diagnostics Precursory uplift Initial LIP Time-progressive volcanic chain Deep mantle seismic anomaly

7 Uplift contemporaneous, fast, permanent Jones (2005) m m m m m m m

8 LIP Not one, but two

9 Iceland LIP started ~ 30 Ma Area = ~ 500,000 km 2 LIP # 2

10 Time-progressive chain

11 Seismic anomaly Ritsema et al. (1999) model of Bijwaard & Spakman (1999)

12 Now I’ve got that off my chest, let’s turn to some problems 1.Complex spreading 2.An Easter-type trapped microplate? 3.Composition of the crust and mantle

13 1. Complex spreading How? Why? What is the way forward?

14 1. Complex spreading

15 1. Complex spreading

16 1. Complex spreading

17 2. A trapped microplate beneath Iceland

18 3. Composition of crust and mantle

19 3. Composition of crust and mantle

20 3. Composition of crust and mantle Iceland Shelf

21 3. Composition of crust and mantle  mantle-lowercrust ~ 100 kg/m 3 Composition unknown Source of Icelandic lavas partly recycled surface materials –crust? –lithosphere? –how much? ~ 10%? (Sobolev et al., 2007) –where does microplate fit in?

22 “To summarise the current state of knowledge…” We know a lot, but understand little

23 Resources

24