0198566123.pdf

Fig. 2.14. Beginning in the Eocene, left-lateral fault-
ing along the northern Caribbean plate margin
slowly moved Jamaica eastward relative to the
North American plate, the island varying in size
and becoming increasingly distant from the North
American continent in the process. More crucially
still, from a biogeographical perspective, in the
Late Eocene, it was entirely submerged, with exten-
sive marine deposits being laid down and total
subsidence in Jamaica amounting to some 2800 m,
before its eventual re-emergence as an island in the
early Miocene. The uplift began in the northern and
northeastern coastal region, with general uplift
beginning in the middle Miocene. Maximum uplift
and faulting occurred in the Pliocene (the final
stage of the Tertiary), with as much as 1000 m of
uplift in the Blue Mountains area since the middle
Pliocene. Even after the major period of emergence
began, the island continued to move away from
Central America, possibly by as much as 200 km in
the past 5 million years.
The message that must be drawn from this and
the foregoing sections is that such basic environ-
mental features as island elevation, area, geology,
location, isolation, and climate are each subject to

significant change in the long term. On evolution-

ary time scales, volcanic islands in particular are

remarkably dynamic platforms. If we are to

understand the biogeography of such island sys-

tems, it is clearly necessary to integrate both

historical and contemporary ecological factors

(e.g. Stoddart and Walsh 1992; Wagner and Funk

1995; Price and Elliott-Fisk 2004; Price and

Wagner 2004).

2.4 The physical environment of islands

Topographic characteristics

Topographic characteristics for a selection of islands

in the New Zealand area are provided by Mielke

(1989), who notes that, although the largest islands

have the highest peaks, smaller islands display no

consistent pattern (Table 2.4). In fact, topographic

characteristics depend on the type of island.

Volcanic islands tend to be steep and relatively high

for their area and, through time, become highly dis-

sected through erosion (Fig. 2.15). As long ago as

1927, Chester K. Wentworth calculated the age of

the Hawaiian volcanoes as a function of the degree

32 ISLAND ENVIRONMENTS

25 Ma

(a)

20 Ma

Ku

PH

PH

15Ma

5 Ma

10 Ma

Li La

La

LP

Ma

Ne

Ni Ka

G

G

LP

Ne

Ma

Ni Present

MN

Ha

Ka

Oa

G

Li

Figure 2.13(a) Hawaiian island configurations at 5 Ma intervals. Ku: Kure, PH: Pearl and Hermes, Li: Lisianski, La: Laysan, Ma: Maro, G:
Gardner, LP: La Perouse, Ne: Necker, Ni: Nihoa, Ka: Kauai, Oa: Oahu, MN: Maui Nui, Ha: Hawaii. (Redrawn from Price and Clague, 2002, Fig 3).
(b) Distribution of estimated island maximum altitudes over time (black areas 2000 mASL, dark grey: 1000–2000 m, light grey: 500–1000 m,
white:500 m) (Redrawn from Price and Clague 2002, Fig. 2a).

(b) 25

20

15

10

5

0

5 101520253035

Number of volcanic peaks