**1. Introduction**

Monogenetic volcanoes (typically ≤1 km3 and ≤ 102 years) are usually distinguished as dominantly formed by either magmatic or phreatomagmatic explosive activity and accompanied effusive processes. The magmatic explosive eruptions typically build scoria or spatter cones, while explosive phreatomagmatic eruptions characteristically form tuff cones, tuff rings, maars and maar-diatremes [1]. Associated with either activity, effusive emissions forming lava domes and lava flows are also common; consequently, these products are part of the mentioned volcanic edifices [2–4]. Frequently, individual effusive monogenetic emissions are also released into the Earth's surface, thus forming exclusively, or dominantly, effusive monogenetic volcanoes (e.g. [5]). In spite of this, they are usually not part of the monogenetic classification schemes (e.g. [1, 6, 7]), although many have been widely studied (e.g. [8–16]; among many other studies).

Lava domes in general have been mostly described as part of eruptions in polygenetic, intermediate to acidic volcanoes (e.g. [17]). From there, several types have been defined. Based on the growing mechanism, they are either endogenous whether they expand by intrusion of new magma or exogenous whether they enlarge by extrusion of it [18]; they are also called cryptodomes whether the magma did not reach the surface [19]. Furthermore, based on the geoform, they have received different names such as tortas, platy, axisymmetric, lobate, spines or peléean-type, upheaved plugs, viscous coulées lava streams, among others [17, 20–22]. As minor centers (i.e. as monogenetic volcanoes), the only classification that exist for our knowledge, is that outlined by De Silva and Lindsay [23] who grouped them in: 1) lava domes or tortas, 2) coulées, 3) peléean, and 4) upheaved plugs, based on their morphology. Individual monogenetic lava flows, in addition, are not part of this or any other classification scheme with the exception of the scutulum, low shields or small-shields (cf. [24, 25] that are mentioned by De Silva and Lindsay [23] within the mafic monogenetic volcanoes classification.

It is worth mentioning that the concept of "monogenetic" volcanism has even been considered in association with 1) Large Igneous Provinces (LIPs) that are overwhelmingly effusive, but formed in very short period of time in single flare ups [26], or 2) effusive dominated fields that are smaller than typical Large igneous provinces but significantly bigger than a "normal" monogenetic field [25]. In this work, however, we refer to small-volume monogenetic volcanoes, understood as small magma batches reaching the surface dispersed and episodically.

We herein propose the expansion of the existing monogenetic classification scheme after including the effusive volcanoes based on the above mentioned. This classification is based on their geoform, similarly to the explosive volcanoes. Furthermore, we provide a framework of the processes that act during the magma ascent and cause differentiation to produce intermediate to evolved volcanic products. Thus, we outline magmatic plumbing system options, which include crustal magma reservoirs as zones for detaching magma batches. Finally, we provide an overview of this particular poorly known volcanism worldwide, contributing to the monogenetic comprehension for future studies.
