Geoscience studies in the Maltese Islands: a gateway to the Central Mediterranean region

Geoscientific field

We identified 16 research themes, reported below in alphabetical order, and assigned to them the selected papers:

- Engineering geology

- Geoarchaeology

- Geochemistry

- Geoheritage

- Geomorphology

- Geophysics

- Georesources

- Historical geology

- Hydrology and Hydrogeology

- Mineralogy

- Oceanography and Marine geology

- Palaeontology and Palaeoecology

- Petrology

- Stratigraphy and Sedimentology

- Structural geology

- Multidisciplinary (including also significant contents outside geosciences; e.g., ecology, environmental and climate issues).

Our analysis reveals that 150 papers deal extensively with more than one geoscientific field (see Fig. 3). Geomorphology is the largest segment of the papers found, accounting for 20.2% showing an increased interest in this field in the last decade. The field of Stratigraphy and Sedimentology accounts for 14.6%, while Palaeontology and Palaeoecology, together with Structural geology, both account for 14.4% of the papers. Geophysics follows closely, with 10.7% of the total. Engineering geology represents the 6.4% of the papers. Oceanography and Marine geology account for 4.8% of the papers. The geoscientific fields of Geochemistry, Hydrology and Hydrogeology and Georesources contribute to 2.7%, 2.6% and 2.1% respectively to the total. The field of Geoarchaeology corresponds to 1.7% of the papers. Geoheritage, Mineralogy and Multidisciplinary share the low percentage of 0.9. However, the interest for geoheritage showed a remarkable increase in recent years. Historical geology and Petrology have a minimal presence, each representing 0.5% of the overall distribution.

Fig. 3

Time distribution

We carried out an analysis of the temporal distribution of publications with reference to the geoscientific fields outlined above (Fig. 3). We computed cumulative curves (Fig. 4) that show a general increasing trend of publications about the Maltese Islands, for the timeframe considered. The graph highlights diversified trends among geoscientific fields showing an increasing interest in Geomorphology, which has gained momentum during the last decade. In the field of Palaeontology and Palaeoecology, there is a notable activity between 1860 and 1900 followed by near stability until 1970, after which there has been a significant growth to the present day. The field of Stratigraphy and Sedimentology shows two major peaks, one around 1890 and the other between 1980 and today. Structural geology seems to have attracted most interest since the late 1970s, while attention to Geophysics and Engineering geology have been increasing in the last two decades. The zoomed in inset shows other research fields with a slower increase rate (Fig. 4).

Fig. 4

Keyword frequency and distribution

We generated word clouds (Fig. 5) for each geoscience field based on the frequency of keywords from selected papers. The word clouds included keywords that appeared in more than one paper. Word clouds provide a quick and visual representation of prominent keywords, aiding in the identification of key themes across the reviewed papers.

Fig. 5

The size of words in the cloud is proportional to their frequency, aiding in discerning which concepts and thematic areas received greater emphasis in the analysed literature. This approach enabled the identification of geoscientific fields sharing similar keywords.

Keywords associated with Hydrology and Hydrogeology have some overlap with those of Structural geology, including terms such as ‘normal fault’, ‘carbonates’, ‘fluid flow’, ‘fault zone’, ‘fault zone architecture’, and ‘deformation mechanism’. In addition, the keyword ‘normal fault’ is shared with Geophysics. The latter shares terms such as ‘lateral spreading’, ‘landslide’ and ‘GPR’ with Geomorphology. Geomorphology’s keywords also partially overlap with those of Engineering geology sharing terms such as ‘landslides’, ‘SAR interferometry’, ‘rock spreading’, ‘risk assessment’, ‘susceptibility’, ‘GPR’, and ‘GPS’. The geoscience fields of Geophysics and Engineering Geology include the term ‘geomorphology’ among their keywords. Stratigraphy and sedimentology share some keywords with Palaeontology and Palaeoecology, such as ‘Miocene’ and ‘biostratigraphy’.

Location of study areas

We classified the selected papers based on the location of the investigated study areas in (i) onshore, (ii) offshore and (iii) integrated onshore-offshore papers.

We then examined the distribution of these study areas with reference to the various geoscientific fields, as illustrated in Fig. 6. Research on the Maltese Islands focus on onshore study areas, with the exception of Oceanography and Marine geology. Structural geology and Geophysics are the only ones where the number of papers on onshore and offshore study areas is almost equal. Meanwhile, Multidisciplinary, Geoheritage, Petrology and Historical geology refer exclusively to onshore regions. Palaeontology and Palaeoecology, Hydrology and Hydrogeology, and Mineralogy deal exclusively with onshore and offshore areas, and no evidence of integrated terrestrial and marine data was observed. The field of Geomorphology presents the largest number of papers integrating terrestrial and marine datasets.

Fig. 6

Scholarly collaboration metrics

Scholarly collaboration metrics provides insights into the collaboration degree within each of the considered geoscientific fields. With reference to single disciplines, we did not consider multiple authorships of a given author in the total count. For instance, if a single author contributed to multiple papers within a specific geoscientific field, that author was considered only once, ensuring that individual authors were not double-counted based on the number of papers they published. This approach helped provide a more accurate representation of the number of unique authors involved in the collaborative efforts within the geoscientific field. Table 1 offers an overview of research collaboration within each geoscientific field. It includes, among other values, also the data relating to indicators derived from geoscientific fields which overall total a number of papers of less than ten (namely, Geoheritage, Historical geology, Mineralogy, Petrology). This was done to ensure a comprehensive illustration of the results of the scholarly collaboration metrics. However, the results of the collaboration metrics for the geoscientific fields that have fewer than ten papers are not described further. In fact, the low number of papers retrieved for these fields deems them non-representative for the study of collaboration.

From the results presented in Table 1 and in Fig. 7, it is evident that some geoscientific fields, including Geophysics, Engineering geology, and Geomorphology, show a notable tendency to have the lowest number of single-author papers compared to the total paper count. This trend suggests a propensity towards collaboration within these specific fields.

Fig. 7

The Authors per paper indicator represents the ratio between the overall number of authors in a particular geoscientific field and the corresponding total number of papers. The highest values of this indicator correspond to fields characterised by a higher number of authors relative to the total number of papers. Greater ratios of Authors per paper may be indicative of fields where a greater number of authors collaboratively contribute to individual papers compared to the overall document count. This suggests distinct approaches to collaboration among the different geoscientific fields.

An analogous trend is shown by the Authors’ Collaboration Index, with higher values suggesting that, on average, there is a high variety of authors contributing to each multi-authored document. This could indicate a high level of collaboration within the geoscientific field implying the involvement of many different authors. A low Authors’ Collaboration Index implies that, on average, there is a fewer diversity of authors among multi-authored documents.

Examining Table 1 and Fig. 7, and focusing on geoscience fields with a total number of articles ≥ 10, which ensures the most representative indices, significant insights emerge. Geomorphology is the geoscientific field with the highest number of publications (119), frequent collaborations (98) and the lowest Authors’ Collaboration Index (1.9). Geoarchaeology has the lowest number of publications (10), shared with Geochemistry for single-author articles (3) and Georesources for multi-author articles (7). The geoscience field of Georesources, with the lowest number of authors (27), contrasts with Structural geology, on which most authors focused (210). Palaeontology and Palaeoecology stand out with the highest number of publications per single author (55). The field of Oceanography and marine geology has the highest Authors’ Collaboration Index (5.2).

Country of authors and networking

The collaboration between authors, based on their affiliation, was also analysed through a country collaboration network (co-authorship) in order to facilitate understanding of international connections (Fig. 8).

Fig. 8

The plot highlights that the authors from Italy and the United Kingdom are those with whom Maltese geoscientists have most frequently collaborated (55 and 20 collaborations respectively). The plot distinctly illustrates the central role of scientific collaboration between Italy and Malta in this specific research domain. Spain (8 collaborations), USA (7 collaborations), and Germany (7 collaborations) show a high degree of connection with the Maltese geoscience community.

Geoscientific field

Over time, the Maltese Islands have attracted numerous scholars due to their significant geological importance. As described by Zammit-Maempel (1989), geoscientific research started in the second half of the 19^th century thanks to the so-called pioneers of Maltese geology, who mainly focused on the Stratigraphy and Sedimentology of the Maltese Islands (e.g., Adams, 1863; Cooke, 1893a, 1896a), Palaeontology and Palaeoecology (e.g., Spratt, 1867a; Adams, 1879; Cooke, 1890, 1893c) and Structural geology (e.g., Spratt, 1854), which are often treated in parallel even within the same papers. Their focus was on the geological formations of the Maltese Islands, emphasising their stratigraphic features, fossil content and the tectonic mechanisms responsible for their deformation.

The first half of the 20th century saw a reduction in geoscientific publications related to the Maltese Islands likely due to the occurrence of the two world wars. However, the publications of this period were mainly focused on Palaeontology and Palaeoecology (Lemoine & Douville, 1904; Bate, 1916, 1935; Douville, 1926; Trechmann, 1938) and on Stratigraphy and Sedimentology (Hobbs, 1914; Rizzo, 1932a, 1932b; Trechmann, 1938; Reed, 1949). The second half of the 20th century marked a resurgence of geoscientific interest in the Maltese Islands which continues to produce new contributions. The increase in geoscientific attention and corresponding scientific publications related to the Maltese Islands can be attributed to a confluence of factors. Technological advances played a key role, facilitating more thorough and precise investigations. In addition, increased environmental awareness underscored the imperative to safeguard and sustainably manage ecosystems of geological and environmental importance, fuelling scholarly interest. Finally, the growing trend in the global scientific community toward international collaboration and knowledge sharing contributed significantly to the increase in research on the Maltese Islands. Our investigation revealed the importance of geomorphological investigations conducted on the Islands, especially during the last decade (Fig. 3). This research interest is mainly motivated by the Islands’ susceptibility to coastal landslides (e.g., Soldati et al., 2019; Rizzo et al., 2020; Devoto et al., 2021; Mantovani et al., 2022) and coastal erosion (e.g., Farrugia, 2017; Micallef et al., 2018; Causon Deguara et al., 2023), processes which are favoured by sea-level rise (e.g., Biolchi et al., 2011; Furlani et al., 2017; Prampolini et al., 2019; Vandelli et al., 2023), local topography and geological composition (e.g., Spratt, 1854; Pedley et al., 1976; Lorenz & Mascle, 1984). In many cases, the field of Geomorphology is treated in parallel with Engineering geology, with the aim to deepen the understanding of the previously mentioned processes and, consequently, to improve the management and planning of coastal areas. In particular, this interest has gained more importance in recent years, driven by a growing awareness of the practical implications for adaptation, mitigation measures and sustainable development issues, thus underlining the need for a more comprehensive understanding of the geomorphology of the Maltese Islands.

The field of Stratigraphy and Sedimentology is also showing considerable interest today, driven by the peculiar geological characteristics of the region. The interest is to understand the sedimentary succession in the Late Oligocene-Miocene within the Islands (e.g., Baldassini & Di Stefano, 2017; Bialik et al., 2021). In many cases, papers dealing with Stratigraphy and Sedimentology also delve into the Palaeontology and Palaeoecology, and the Structural geology of the Maltese Islands. Indeed, the latter boast a rich fossil record (e.g., Hojjatzadeh, 1978; Bosence & Pedley, 1982; Bosence, 1983; Gatt & De Angeli, 2010; Nicholl et al., 2020), providing insights on biostratigraphy (e.g., Mazzei, 1985; Foresi et al., 2002, 2007; Gruszczyński et al., 2008; Bianucci et al., 2011; Catanzariti & Gatt, 2014), past ecosystems (e.g., Cooke, 1893c; Pedley et al., 1976, 1978; Pedley, 1979; Brandano et al., 2008, 2009), biodiversity (e.g., Zammit-Maempel, 1969; Rehfeld & Janssen, 1995) and how the latter responded to environmental changes over geological time scales (e.g., Zammit-Maempel, 2007; Brandano et al., 2009). As for Structural geology, the aim is mainly to provide insights into the deformation processes that have shaped the geological framework of the Islands over time (e.g., Hobbs, 1914; Pedley et al., 2002; Scerri, 2019).

Time distribution

The cumulative curve of the number of papers in geoscientific fields over time (Fig. 4) provided a comprehensive overview of the evolution of the geoscientific research landscape on the Maltese Islands. Overall, the analysis revealed a general increase in the number of articles in all geoscientific fields, indicating a growing interest in geoscientific research in the Maltese Islands. Within specific areas, the following trends were observed:

- A significant and steady increase in the number of publications dealing with the Geomorphology over the last decade suggested a growing interest in understanding the evolution of the Maltese landscape, for the definition of adaptation and mitigation measures made necessary by the climate-related risks to which the Islands are subject;

- A peak between 1980 and the present day was evident in the field of Stratigraphy and Sedimentology, and could be related to periods of increased geological exploration or methodological advances favouring research activity in these areas;

- The special interest in Palaeontology and Palaeoecology from 1970 to the present day could be attributed to technological advances that have led to a renewed interest in discoveries in the palaeontological history of the Islands;

- A growing interest in Structural geology has been observed since the late 1970s, indicating a shift in focus towards understanding the tectonic processes and deformation history of the Maltese Islands;

- The last two decades have seen an increase in attention also in the fields of Geophysics and Engineering geology, which may reflect the contemporary emphasis on applications of adaptation and mitigation structures and in environmental monitoring;

- Recently, there has been a relatively significant increase in the number of geoheritage papers regarding the Maltese Islands (e.g., Coratza et al., 2016; Selmi et al., 2022). In the past few years, the Islands’ efforts to promote geoheritage conservation have included raising awareness of the importance of geological features, developing geotourism and implementing measures to ensure the sustainable management and protection of these valuable geological assets. These efforts are particularly important due to the challenges posed by extensive urbanisation and artificial land cover (cf. Pace et al., 2023), making the conservation and sustainable management of geoheritage a priority for the country.

The trends observed in publication activity in the different geoscientific fields offer valuable insights into the dynamic nature of scientific investigation in the Islands.

Keyword frequency and distribution

From the world clouds (Fig. 5) it emerged that researchers in Engineering geology, Geomorphology, and Geophysics demonstrate a shared interest in coastal landforms and processes (e.g., Devoto et al., 2012, 2020; Prampolini et al., 2017; Galea et al., 2018; Rizzo et al., 2020, 2022; Vandelli et al., 2023). Research within these geoscientific fields focused on coastal landslides, namely on diffused rock spreads and block slides which were not mapped and monitored until 2008 (e.g., Magri et al., 2008; Devoto et al., 2020, 2021; Mantovani et al., 2022). A number of geomorphological studies focused on extreme wave events and related deposits (e.g., Causon Deguara & Scerri, 2019; Mottershead et al., 2020). Hydrology and Hydrogeology both contributed to the examination of fluid flow within normal faults affecting the carbonate rocks of the Maltese Islands (e.g., Micallef et al., 2011; Dimmen et al., 2017). Geochemical studies primarily focused on the weathering of the limestones (e.g., Cassar & Vella, 2003; Bianco, 2021; Roussel et al., 2021). Stratigraphy, sedimentology and palaeontology collaboratively investigated the Miocene sedimentary successions (e.g., Bianucci et al., 2011; Baldassini & Di Stefano, 2015; Scerri, 2019) and carbonate platforms (e.g., Brandano et al., 2019; Bialik et al., 2021; Gatt, 2022). Geoscientific research appeared extremely interconnected, highlighting the considerable potential for collaboration and interdisciplinary research, which are essential for deepening the understanding of complex geological phenomena.

Location of study areas

The literature analysis revealed that most of the studies were focused on onshore areas. This reflected especially in the early geoscientific production regarding the Maltese Islands witnessed by the pioneeristic studies carried out in the 19^th century (Zammit-Maempel, 1989). However, when dealing with Structural geology and Geophysics, an equal interest emerged for both onshore and offshore regions. In particular, Structural geology exhibited a certain interest in submarine structural and tectonic features, notably those situated in the Sicily Channel, encompassing the Malta Plateau and Escarpment, the Pantelleria Graben, the Malta Graben and the Linosa Graben, which are among the main tectonic structures in the Central Mediterranean Sea (Fig. 1A). Additionally, quite a large number of geomorphological studies focused on the submerged landscape of the Maltese seabed (e.g., Foglini et al., 2016; Prampolini et al., 2018, 2019). Turning attention to Geophysics, its methodologies, particularly those involving sonar sounding systems and seismic reflection techniques, played a pivotal role in deciphering submerged features and/or onshore areas (e.g., D’Amico et al., 2022).

It is widely recognised how integrating terrestrial and marine datasets can be beneficial in geo-environmental studies (Prampolini et al., 2020). Nevertheless, the literature review reveals that only a limited number of studies embraced this integration. Thus, there is a clear opportunity for future endeavours to focus on advancing this direction. Another opportunity arises from the potential for acquiring novel insights into the unexplored submerged geoheritage of the Maltese Islands, as documented for other Mediterranean submarine areas (cf. Coratza et al., 2019).

Scholarly collaboration metrics

The outputs of the scholarly collaboration analysis revealed that most of the investigated literature is the result of a collaborative effort. Among other indicators included in Table 1 and Fig. 7, the Authors’ Collaboration Index provided a quantitative measure of the collaboration degree within a specific geoscientific field. It was calculated as the ratio between the number of Authors of multi-authored papers (eliminating authors’ repetitions) and the number of Multi-authored papers (cf. Literature review outputs). A high Authors’ Collaboration Index implied a rich diversity of authors contributing to multi-authored papers in a specific geoscientific field. This diversity suggested a broad spectrum of expertise and methodologies involved in a certain field of the geoscientific research, as in the case of Oceanography and Marine geology, Geochemistry, Geoarchaeology and Multidisciplinary studies. A low Authors’ Collaboration Index may suggest a narrower range of authors involved in multi-authored papers. This is the case of the Geomorphology geoscientific field where there was a clear opportunity to enhance collaboration by expanding the author network including diverse perspectives and interdisciplinary approaches.

Country of authors and networking

The examination of the collaboration network among countries, as detailed in the Literature review outputs, revealed that the authors with Maltese affiliation most frequently collaborate with scientists from Italy and the United Kingdom in the field of geosciences. The geographic proximity of Italy and Malta may favour exchange among scientists, facilitating logistical aspects of collaboration. The linguistic connection adds another layer to this collaboration. The historical use of Italian as the third language in Malta, and its status as an official language until 1936 (Caruana, 2013), likely facilitated the communication and collaboration between Italian and Maltese scientists. The current economic and tourism exchanges between Italy and Malta may play a role in enhancing further scientific collaboration. Italy’s position as the third-largest import partner for Malta (The Observatory of Economic Complexity, 2023) reflects a robust economic relationship. The significant number of Italian tourists, second only to UK tourists (OECD, 2022), may provide opportunities for cultural and scientific exchanges. Additionally, Malta serves as a favoured destination for Italian students attending English language courses, further enriching the multifaceted nature of Maltese-Italian collaboration. It is worth mentioning that this comprehensive collaboration extends beyond geographic, linguistic, and economic connections, encompassing a close political relationship evident through official exchanges and bilateral agreements (Caruana, 2013).

Similarly, the intense collaboration between Malta and the United Kingdom could be attributed to historical factors as well, specifically Malta’s status as a British colony until its independence in 1964 (Schembri et al., 2020). This historical connection is further emphasised by the enduring influence of the English language, which continues to be one of the official languages of Malta. The shared history and linguistic ties likely contribute to the robust scientific collaboration observed between Malta and the United Kingdom, reflecting a historical continuum of scholarly exchange.