**2. Geologic settings**

dating of the basalts of the Kassa volcanic field has revealed young ages spanning from 2.5, 1.97, 1.66, 1.39 to 1.34 Ma confirming the recent but short interval and multiple successive episodes of eruptions associated with volcanic activity in the region. Similar ages in the range of 2.1–0.9 Ma have been reported from basaltic rocks from the Benue Trough and a dolerite dyke from the region [1]. These same range of ages (of 2.83–0 Ma) have been obtained on basaltic rocks from the near-by Cameroon Volcanic Line (CVL) [1]. The Jos Plateau basalts vary in composition from basalt proper to trachyandesitic varieties of alkaline basalt magma series and some tholeiitic affinity [2]. Contrarily to the general notion that volcanoes are only associated with plate margins alone, the volcanoes in Nigeria are emplaced within the continent, associated with mantle Hot Spots. Records of gas emissions at Lakes Monoun and Nyos in Cameroon Republic in 1984 and 1986 respectively destroyed

*Forecasting Volcanic Eruptions*

**Figure 1.**

**6**

*Locations of the Jos and Biu Plateaux Volcanic Provinces, Nigeria.*

An understanding of the geology is important in studying natural hazards related to volcanism because the geology influences tectonic movement which leads to the disequilibrium of the ecosystem and other environmental components.

The Nigeria-Cameroon Volcanic Provinces lie within the Pan-African collision belt of West Africa (**Figure 1**). In Nigeria, the volcanic provinces (Jos Plateau, Biu Plateau, Benue Valley, etc.) are confined to the northeastern and central regions [4]. The volcanic provinces are characterized by numerous volcanic cones and lava flows consisting of alkaline olivine basalts together with less important trachyte and phonolite intrusive rocks [5].

Apparently, the large volcanic province of Nigeria suggests that volcanic activity during the Quaternary, was intense on the Jos Plateau, the Benue trough and along the northeast to southwest Cameroon line. Like the Jos Plateau volcanic regions, most of the main volcanic provinces such as the Bamenda Highlands, the Mambilla Plateau and the Adamawa Plateau are characterized by basement uplift [5].

The Cameroon Volcanic Line which extends from the Gulf of Guinea, Island of Annobon, Sao Tome and Principe and Fernando Po splits into two branches, one extending into northern Nigeria forming the Biu Plateau while the other extending eastward forming the Ngoude Plateau of Eastern Cameroun (**Figure 1**). Thus, in Nigeria, the volcanic provinces occur as relicts of volcanism in the form of scattered volcanic plugs and cones in some cases [5]. On the relatively uplifted Jos Plateau region, volcanic rocks are represented by volcanic cones and calderas [2].

Some of these cones generally rise only few hundred meters above the Plateau surface and are steep-sided with a central crater which may measure up to 450 m usually emerging at a breached in the crater wall. They are mainly built of basaltic scoria, volcanic ash, lava and with some variety of inclusions.
