Topology
The island comprises a large central lowland of limestone with a relief
of hills surrounded by a discontinuous border of coastal mountains which
vary greatly in geological structure. The mountain ridges of the south
are composed of old red sandstone separated by limestone river valleys.
Granite predominates in the mountains of Galway, Mayo and Donegal in the
west and north-west and in Counties Down and Wicklow on the east coast,
while a basalt plateau covers much of the north-east of the country. The
central plain, which is broken in places by low hills, is extensively
covered with glacial deposits of clay and sand. It has considerable areas
of bog and numerous lakes. The island has seen at least two general glaciations
and everywhere ice-smoothed rock, mountain lakes, glacial valleys and
deposits of glacial sand, gravel and clay mark the passage of the ice.
The highlands of the north, west, and south, which rise to more than 3,000
ft (914 m), are generally barren, but the central plain is extremely fertile
and the climate is temperate and moist, warmed by southwesterly winds.
Ireland's greatest length is 485 km (302 miles) and it is 304 km (189
miles) at its widest point.
Among Ireland's natural advantages is 5,631 km (3,500 mi.) of coastline,
so indented that you are never more than 70 miles from the sea. Add to
this the 800 lakes and rivers of inland Ireland and you can be fairly
certain of being in sight of some body of water anywhere in Ireland!
The highest mountain is Carrantuohill (1,040 metres/3'414 feet), near
Killarney in County Kerry.
The longest river is the Shannon (370 km/230 miles, including estuary)
which opens at the sea in county Limerick.
The largest lake is Lough Neagh (396 ssq km/153 ss.quare miles) in the
North and is bordered by counties Armagh, Down, Antrim, Derry and Tyrone.
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