The Geological Heritage of Príncipe Island (West Africa)

Abstract

The Príncipe Island is in the Gulf of Guinea, along the Cameroon Volcanic Line (West Africa). It is known worldwide for its biodiversity for whose conservation there is strong national and international consensus. But its geodiversity has played and continues to play a very important role in creating this unique habitat in sub-Saharan Africa, and represents an important asset in promoting local tourism, with a focus on the geological history of this remote island. The purpose of this study is to provide a comprehensive synthesis that is both up-to-date and inclusive, incorporating all the fundamental information and references on the geodiversity and the geological heritage of the Príncipe Island. The geological heritage of Príncipe Island is represented by ten geological heritage sites of different types (volcanological, geomorphological, sedimentological, and stratigraphical), and five viewpoints, whose geoheritage contents make it possible to support a narrative about the geological history of the Cameroon Volcanic Line that is of major relevance for the development of geoeducational resources and potentially appealing to fostering regional geotourism. Príncipe geological heritage sites were inventoried and assessed using the same qualitative methodology previously applied to the geological heritage of São Tomé Island, therefore making it possible to complete the country’s national inventory of geological sites, as well as to enrich the representation of African geoheritage among the world’s list of geological heritage sites.

1. Introduction

The Earth exhibits a considerable degree of natural diversity, encompassing both biotic and abiotic elements. The latter are also referred to as geodiversity and are defined as the natural range of geological, geomorphological, soil, and hydrological features [1]. The concept of geodiversity is often considered to be the foundation of biodiversity. The abiotic conditions provide the fundamental framework for the living world, facilitating the emergence of variation through the creation of distinctive topographical and climatic conditions [2,3].

The concept of geodiversity valuation is derived from the necessity to provide support for the conservation of natural resources [4]. The integration of geodiversity information into biodiversity research and conservation has the potential to enhance our understanding of biodiversity patterns and dynamics, as well as to improve the efficacy of biodiversity protection through the implementation of a coarse-filter conservation strategy [5].

Geological heritage is defined as concrete examples of geodiversity that are specifically identified as having exceptional scientific, educational, tourist, or cultural significance [4,6]. Research indicates that the social application of geology can significantly contribute to sustainable development, geoeducation, and geotourism, providing substantial benefits to any region. This is particularly crucial for African nations, where global attention on geoheritage is limited, and there remains a wealth of opportunities for exploration [7].

The “Cameroon Volcanic Line” (CVL) is characterized by a linear chain of islands that extend across the Gulf of Guinea, converging to form an arc of peaks that traverse Cameroon. This 1000 km long line of ten volcano-capped swells represents a unique geological topographic structure crossing both ocean and continent and is known as the African Pole of Rotation. This is one of the 20 African Alive Corridors, which provide specific milestones to reconstruct and tell the African autobiography [8,9,10].

As a node (18: Príncipe “Einstein’s Theory of Relativity”) of the “African Pole of Rotation” Corridor, revealing the geoheritage of this island could enhance the Corridor’s ability to establish a sustainable tourism route, thus fostering growth across all sectors of tourism, education, and entrepreneurship, as well as benefiting the broader community [9]. Furthermore, the promotion of geotourism as a strategic economic activity on the island can lead to the expansion and diversification of the current tourism offer, as the marketing of the island is based, above all, on the country’s extraordinary biodiversity [11,12].

The initial approaches to the geoheritage of the Democratic Republic of Sao Tome and Principe were developed in São Tomé Island ([13] and references therein) employing an integrated evaluation system that is qualitative in nature and is based on the geoheritage contents that geosites may display. This methodology was later adopted in a preliminary way at Príncipe Island [14], thus facilitating a comparative analysis between the two islands [15]. This instrument is particularly well suited to the entire heritage of the archipelago of Sao Tome and Principe, as well as the oceanic part of the CVL.

In the first article, which highlighted the island’s most emblematic geosites [14], it was recognized that a number of these sites are incorporated within the Biosphere Trails. These routes serve to emphasize the significant values of the island’s abundant biodiversity, a factor that led to its designation as a Biosphere Reserve by UNESCO in 2012.

The purpose of this research is to offer a global viewpoint on the natural heritage of Príncipe Island, merging the geodiversity aspect with biodiversity, and to carry out an in-depth analysis of the most important abiotic factors of the island, which was established 31 million years ago, consequently supporting the formation of a rich and unique biodiversity and geodiversity.

Príncipe geological heritage sites were inventoried and assessed using the same qualitative methodology previously applied to the geological heritage of São Tomé Island. This facilitated the completion of the country’s national inventory of geological sites, as well as the enrichment of the representation of African geoheritage among the world’s list of geological heritage sites.

Furthermore, it is a fundamental element of the 2030 Agenda, as the advancement of knowledge in the field of geosciences has the potential to play a pivotal role in the preservation of geodiversity and will contribute to the realization of the United Nations’ objectives for Small Island Developing States (SIDS). It will facilitate awareness and appreciation of geoscience among tourists and communities living in areas displaying abundant geological heritage [16,17,18,19].

2. Study Area

The islands of Sao Tome and Principe constitute a volcanic archipelago, comprising two principal islands and several smaller islets located in the Gulf of Guinea (West Africa), along the Cameroon Volcanic Line (CVL). The island of Príncipe is the smallest in the archipelago, with a total area of 136 km² and situated close to the equator line at 1°36′ N–7°23′ E (Figure 1).

Due to changes in the stress field in the nearby high lithosphere, the CVL was formed in the continental lithosphere at 65 My [8,20]. It is subdivided into two distinct sections: the continental and the offshore section. The last one is situated at the apex of an asymmetrical arc, measuring 200 km in length and 3 km in height. The region contains a substantial volcanic center, comprising igneous material that is predominantly composed of alkaline basalt rings and alkaline basalt granules [21,22,23,24,25] represented by the islands of Annobón (Pagalú), São Tomé, Príncipe, and Bioko [26]. Príncipe Island, the oldest of the three oceanic volcanic islands of the CVL of the Gulf of Guinea, was formed 30.4 Ma.

Lava samples that were dated showed K-Ar radiometric ages of around 30.4 My containing fragments of fresh tholeiite, which is indicative of the island’s evolution through a submarine phase [27]. From alkaline basalt to Hawaiian, the oldest lavas have a range of age between 24 My and 19 My and contain olivine and titanaugite phenocrysts as well as microphenocrysts of plagioclase and titano-magnetite; the groundmass contains microlites of the aforementioned minerals, except for olivine [27,28] (Figure 1). The younger lava series (trachyphonolitic suite) range in age from 5.6 My (nephelinite) to 3.5 My (basanite). It has a matrix of alkali feldspar, nepheline, and apatite, while the phonolitic lavas are porphyries with a fine-stone matrix [27]. The ages of the plugs range from 6.9 (nephelinite) to 3.9 My (basanite) [29]. An Rb-Sr isochron of approximately 5.9 Ma has been established by the younger lava series and all intrusive rocks, which suggests that intrusive rocks and the youngest lava series are linked through cogenetic processes (see Figure 1).

The structural contact between phonolite and trachyte suites separates two lithologic and geomorphologic provinces and it is observable at Praínha (1°38′01.8″ N, 7°21′52″). The island’s northern half is distinguished by a relatively gentle topography, which is predominantly composed of basaltic rocks and frequently covered by laterite crusts, readily observable at the airport (1°40′13.8″ N, 7°24′42.5″ E). In contrast, the southern part of the island is characterized by a mountain range comprising several phonolite peaks and tephrites, with altitudes ranging from 500 to 948 m. This region is home to the island’s primary rainforest [27,30,31]. The island’s rich biodiversity earned the status of Biosphere Reserve awarded by UNESCO in 2012, and its geological heritage were the subject of a generic description in 2023 [14].

3. Methodology

The geoheritage of Príncipe Island has previously been the subject of a summary analysis that highlighted seven geological heritage sites that represent the major geological characteristics of the island [13]. They were evaluated based on a qualitative approach developed by [15], which argues that the geoheritage content displayed by geological objects can be used as a basis for geoheritage assessment, and it is determined by relevance grade (i.e., the importance of the meanings assigned to the objects by the scientific communities) and the abstract perceptiveness (i.e., the public use of the objects).

The qualitative assessment used in this work was previously introduced by [15] as referred in the manuscript and applied in many other papers afterwards by the same authors and other authors.

Relevance grade corresponds to the meaning attributed to the objects by the scientific communities, so the scientific literature reflects this variable. Traditional approaches to geoheritage only consider the scientific value of a geosite, which, in this case, is its relevance grade. However, many geosites can be protected and valued by non-experts, i.e., they represent geoheritage assumed by locals that somehow provide its geoconservation. And the integrated approach here used includes such geosites. The identification of such geosites is based on unconventional data collection (e.g., oral communications, stamps, newspapers, songs, etc.) [32,33]. Priority in geoconservation measures can be determined based on the heritage value obtained through the global qualitative assessment of each geosite (sum of individual ranks) and its vulnerability to natural and anthropic threats ([14] and references therein).

Inventory and assessment of the geological heritage of Príncipe Island were conducted following the steps involving office and field work usually used in geoheritage studies (Figure 2).

Considering the available literature on the island’s geology and the recognition of the different units that make up said geology, several field campaigns were carried out with the aim of identifying potential geological heritage sites to complement the seven previously identified. This step turned out to be very important, as the detailed geological mapping on Príncipe Island is quite old and it has been noted, for example, that some outcrops have already disappeared due to the advance of the jungle. This is the case of a small outcrop of bioclastic limestone located about 1.3 km SE of Santo António, where [35] collected a diversified shallow marine benthic assemblage comprising corals, coralline algae, echinoderms, bivalves, and gastropods, of the Miocene age. The collection is stored at the Science Museum of the University of Coimbra (Portugal) and represents ex situ paleontological heritage of the island, which supports the idea that Príncipe Island was previously surrounded by a reef lagoon bordered by a ring-shaped reef crest and corresponds to the barrier reef stage of coral reef development according to Darwin’s subsidence hypothesis [36].

The selection of the new geological heritage sites followed the same criteria of the first seven, i.e., the representativeness of the island’s geological history, and geoheritage evaluation of each site was based on the relevance grade for scientific communities and the public perception of the geological object under evaluation as reflected by its current use.

The same methodological approach was applied to the geoheritage of the São Tomé Island ([13] and references therein), thereby enabling the comparison of geoheritage values between the two islands, which can easily be extrapolated to other territories of the CVL [37] and/or African countries lacking any geoconservation legislation and where the public awareness about local geoheritage is incipient [7]. Moreover, this method can serve to complement the existing state of conservation in areas that are legally protected for reasons other than geology, as with Príncipe Island, where it was declared a UNESCO World Biosphere Reserve in 2012 [14].

4. Results

The geoheritage of Príncipe Island is represented by ten geological heritage sites and five viewpoints, whose integration enables the formulation of a coherent narrative about the geological history of the island and facilitating the comprehension of the various geological episodes that took place throughout the CVL. By exploring these 15 geological heritage sites, visitors can gain insight into the island’s 31-My history, embarking on a journey that unveils the enigmatic facets of the island’s geology. The geological heritage sites reveal a variety of remarkable episodes, some more widely distributed and others only sporadically marked. The geological history of the island of Príncipe is a component of a vast and intricate network within the CVL, and as the oldest island in this network, it contains critical markers of this enigmatic volcanic line.

This inventory and assessment were conducted from a regional perspective with the objective of developing a geoconservation strategy as well as a geotourism and education program involving the two islands (Sao Tome and Principe) in the future.

4.1. Geological Heritage Sites Inventorying and Assessment

The present study inventories, characterizes, and evaluates ten geological heritage sites, as well as five viewpoints at Príncipe Island, which are outstanding representatives of the island’s geodiversity and are part of its natural heritage (Figure 3 and

Table 1. Geoheritage types, contents, and relevance grade of the geological heritage sites recognized at Príncipe Island.

Geological Heritage Site/Coordinates	Geoheritage Types	Main Geological Features	Geoheritage Contents	Relevance Grade
Bom Bom Islet 1°42′3″ N, 7°24′13″ E	Volcanic Geomorphological Sedimentological Stratigraphical Tectonic	The geosite represents the interaction of volcanic and tectonic processes with maritime erosion, resulting in the formation of palagonitic breccias. These breccias occur in stratigraphic contact with the oldest series of lavas of subaerial eruptions occurred in the island (24 My), which is cut by strong parallel trachyte dykes, with a thickness of about 5 m in the N 18° E direction ([14] and references therein).	Indicial Symbolic Documental Scenic	National
Sundy Plantation and Sundy Beach 1°40′11″11″ N, 7°23′01″ E	Volcanic Sedimentological Geohistorical	The geosite corresponds to an historic farm stead situated within one of the most significant plantations of the island which were important to observe a solar eclipse that experimentally tested and verified Albert Einstein’s theory of relativity. The coastal strip of the property is composed of a white sandy beach, with outcrops of andesite of the older series that are mixed with phonolitic rocks forming a lava tongue that extends northwards to the basaltic plateau composed of lavas of the younger series; oil seeps flowing through fractures of highly altered phonolitic rocks, accompanied by gas emissions, were recognized in the vicinity (Roça Sundy) and at Duas Águas creek ([14] and references therein).	Indicial Documental Symbolic	National
Praínha 1°38′01.8″ N, 7°21′52″ E	Volcanic Geomorphological Stratigraphical Tectonic	This geosite exhibits the fault plane which corresponds to the structural contact between the northern zone of the island, characterized by a relatively flat topography, and its southern zone, made up of several trachyphonolitic peaks. Seaside phonolite blocks show well defined columnar disjunction.	Iconographic Scenic	Regional
Agulhas Bay 1°36′20″ N, 7°20′32″ E	Volcanic Geomorphological Sedimentological Stratigraphical	In this bay, only accessible by boat, we can see numerous phonolitic and phonolitic trachyte peaks enveloped in dense rainforest, belonging to the intermediate phase of volcanic activity, which characterize the southern portion of the island ([14] and references therein).	Documental Iconographic Scenic	National
Papagaio Peak 1°36′43″ N, 7°23′31″ E	Volcanic Geomorphological	Papagaio Peak, a prominent 680 m high landmark, serves as the backdrop to the city of São António, which is widely regarded as the smallest city in the world. This phonolitic peak represents the intermediate series (6.9 My) and is in the Natural Park of Príncipe, created by Law 7/2006 ([14] and references therein).	Indicial Scenic	National
Oquê Pipi Waterfall 1°35′52″ N, 7°24′50″ E	Volcanic Geomorphological Hydrological	The spectacular waterfall, situated along a structural fault front of approximately 30 m high, enables the recognition of the most recent series of volcanism on the island ([14] and references therein).	Documental Scenic	Regional
Salgada Beach 1°37′56.5” N, 7°27′10.0” E	Volcanic Sedimentological Stratigraphical	The geosite shows the contact between the palagonitic breccia and the ancient series, well visible along the beachfront, where they have formed small natural pools.	Iconographic	National
Évora Beach 1°38′38.1” N, 7°26′21.5” E	Volcanic Stratigraphical Sedimentological	The geosite corresponds to a set of basaltic outcrops cut by a dyke aligned with the orientation of the Cameroon Volcanic Line.	Indicial	Regional
Boi Beach 1°40′49.0” N, 7°27′39.0” E	Volcanic Stratigraphical Sedimentological	The outcrop along the beachfront shows the contact between the palagonitic breccia and the ancient series.	Scenic Symbolic	Regional
Roça Terreiro Velho 1°36′37′′ N, 7°25′13′′ E	Volcanic Geomorphological	The geosite is historically significant as the site of the introduction of the first cocoa tree to the African continent in 1819, thereby establishing a tradition of cocoa cultivation that is currently represented by the prestigious Claudio Corallo cocoa. The site is also home to basaltic geological formations, offering panoramic views of Príncipe Island, including the iconic Boné do Jóquei rock formation, which highlights the symbolic and geological value of the region.	Symbolic Documental Scenic	National
Viewpoint
Viewpoint Site/Coordinates	Geoheritage Types	Main Geological Features	Geoheritage Contents	Relevance Grade
Oquê Daniel (Salaszoy) Viewpoint 1°39′46.5” N, 7°22′44.7” E	Volcanic Geomorphological	This geosite offers visitors the opportunity to observe and appreciate the southern portion of the island of Príncipe characterized by a mountain range comprising several phonolite peaks and tephrites which host the island’s primary rainforest.	Scenic	Regional
São Joaquim Viewpoint 1°37′13” N, 7°22′36” E	Volcanic Geomorphological	This viewpoint provides a privileged perspective of the João Dias (Father and Son) Peaks, constituting one of the most iconic images of Príncipe Island. The various phonolitic towers visible from this site define the topography of the southern region of the island.	Scenic	Regional
Nova Estrela Viewpoint 1° 36′51.2” N, 7°25′37.8” E	Volcanic Geomorphological	The viewpoint corresponds to a postcard of the Príncipe Island, showcasing the “Jockey’s Cap” islet, made up of basalts of the modern series ([14] and references therein).	Symbolic Documental Scenic	National
Antena Viewpoint 1°41′05.7” N 7°26′51.0” E	Volcanic Geomorphological	The viewpoint offers a panoramic perspective of both Macaco Beach and Boi Beach, showcasing prominent outcrops that offer a discerning view of the superimposition of laterites upon more recent series.	Symbolic Documental Scenic	Regional
Banana Beach Viewpoint 1°41′16.1” N 7°26′36.3” E	Volcanic Geomorphological Sedimentological	The most prominent viewpoint in the country, which offers a view of the renowned Banana Beach, is characterized by a white sand beach with substantial blocks of basaltic nature.	Symbolic Documental Scenic	National

).

These include Bom Bom Islet, Sundy Plantation and Sundy Beach, Oquê Daniel (Salaszoi) Viewpoint, Praínha, Agulhas Bay, São Joaquim Viewpoint, Papagaio Peak, Oquê Pipi Waterfall, Nova Estrela Viewpoint, Salgada Beach, Évora Beach, Boi Beach, Antena Viewpoint, Banana Beach Viewpoint, and Terreiro Velho (Figure 4 and Figure 5).

The selection of these geosites was based on several well-defined criteria, including their representativeness of the island’s geological history (i.e., degree of relevance to scientific communities) and their abstract perceptiveness (i.e., public perception of the geological object under evaluation, reflected by its current use; see Table 1).

It is imperative to acknowledge the geoconservation priorities of a given territory to substantiate the political options associated with the respective development strategies (see

Table 2. Geoheritage contents, qualitative assessment, conservation priority and risk of degradation of the geological heritage sites recognized at Príncipe Island.

Geosite	Geoheritage Contents	Qualitative Assessment	Geoconservation Priority	Risk of Degradation
Bom Bom Islet	Indicial Symbolic Documental Scenic	Rank I Rank II Rank III	1st	Natural vulnerability Anthropogenic Vulnerability Public use
Sundy Plantation and Sundy Beach	Indicial Documental Symbolic	Rank I Rank II Rank III	1st	Natural vulnerability Public use
Roça Terreiro Velho	Symbolic Documental Scenic	Rank I Rank II Rank III	1st	Anthropogenic Vulnerability Public use
Praínha	Iconographic Scenic	Rank I Rank III	2nd	Natural vulnerability
Agulhas Bay	Documental Iconographic Scenic	Rank II Rank III	1st	Natural vulnerability
Papagaio Peak	Indicial Scenic	Rank I Rank III	2nd	Natural vulnerability
Oquê Pipi Waterfall	Documental Scenic	Rank II Rank III	2nd	Natural vulnerability
Salgada Beach	Iconographic	Rank II	1st	Natural vulnerability Anthropogenic Vulnerability Public use
Évora Beach	Indicial	Rank I	3rd	Natural vulnerability Anthropogenic Vulnerability Public use
Boi Beach	Symbolic Scenic	Rank II Rank III	1st	Natural vulnerability Anthropogenic Vulnerability Public use
Viewpoint
Viewpoint	Geoheritage Contents	Qualitative Assessment	Geoconservation Priority	Risk of Degradation
Antena Viewpoint	Symbolic Documental Scenic	Rank I Rank II Rank III	1st	Natural vulnerability
Nova Estrela Viewpoint	Symbolic Documental Scenic	Rank I Rank II Rank III	1st	Natural vulnerability
Banana Beach Viewpoint	Symbolic Documental Scenic	Rank I Rank II Rank III	1st	Natural vulnerability
São Joaquim Viewpoint	Scenic	Rank III	2nd	Natural vulnerability Anthropogenic Vulnerability
Oquê Daniel (Salaszoy) Viewpoint	Scenic	Rank III	3rd	Natural vulnerability

). The majority of geosites that have gained recognition tend to experience significant social utilization, as their accessibility often serves as a crucial factor in their transformation into tourist attractions.

The geosites of Bom Bom Islet, Sundy Roça and Sundy Beach, Baía das Agulhas, Nova Estrela Viewpoint, Antena Viewpoint, Banana Beach Viewpoint, and Roça Terreiro Velho have received the highest evaluation rating, thus necessitating the establishment of geoconservation priorities at the uppermost level (see Table 2). These locations represent the most important geological heritage sites regarding their geoheritage significance, necessitating the implementation of geoconservation strategies; they hold particular significance for scientific communities due to their distinctive characteristics and their role in elucidating the geologic history of the island.

These measures prioritize the assessment and oversight of geological heritage, as opposed to its preservation. The four remaining geological heritage sites require the implementation of strategies focused on their valuation and monitoring. Local tour operators and public actors, in partnership with geoconservation specialists, are tasked with the creation and execution of relevant geotourism materials (e.g., field guidebooks, websites, trails, brochures, mobile applications, and interpretative panels) designed for a general audience and providing educational resources that facilitate a comprehensive understanding of Príncipe’s geoheritage. The benefits of this initiative are twofold: it provides visitors with a comprehensive understanding of the island’s geoheritage, and it benefits local residents who can support them during their time on the island.

The following is a concise exposition of the geosites that possess the utmost heritage value.

4.1.1. Bom Islet

Bom Bom is a tiny islet that, at low tide, is revealed as an isthmus. The islet is connected to the mainland by a sandy spit; however, the level of the tide has a significant influence on the feasibility of traversing this expanse (Figure 6). The site is notable for the preservation of the ancient series, resulting from subaerial eruptions on the island that occurred 24 My ago [28]. It is composed primarily by palagonic breccia, the earliest mapped rocks on the island, and basalts intersected by robust, parallel trachyte dykes, exhibiting a notable thickness (approximately 5 m in size, with a N 18° E orientation). In one of these veins, it is possible to observe giant potholes (Figure 6B) and xenoliths (Figure 6E). The islet is characterized by dense wooded areas and a precipitous cliff along its northwest perimeter. Recently eroded conglomeratic deposits and minor siltstone accumulations are observable along the shoreline.

There is an urgent need to enhance and monitor these areas, and the Bom Bom islet, given its popularity and intensive use, faces a heightened risk of physical and marine degradation.

4.1.2. Sundy Plantation and Sundy Beach

The Sundy Plantation and Sundy Beach correspond to an historic farmstead where, in May 1919, Sir Arthur Eddington made an expedition to observe a solar eclipse that first experimentally tested and verified Albert Einstein’s theory of relativity [9,37] (Figure 7). In this sense, it corresponds to the concept of symbolic content described by [15]. In 2023, the site was recognized as part of the country’s indicative list of World Heritage candidate sites. The outcrops show rocks of the older series rocks that are blended with phonolitic rocks, producing a lava tongue that reaches northward to the basaltic plateau, which consists of lava from the younger series [28].

4.1.3. Agulhas Bay

The Agulhas Bay is encircled by a series of phonolitic peaks that evoke the image of needles (“agulhas” in Portuguese) pointing toward the heavens. The various phonolitic towers that characterize the landscape of the southern region of Príncipe Island can be observed from the Agulhas Bay, as well as from both the São Joaquim and Oquê Daniel (Salaszoy) viewpoints (Figure 8). These rocks are also part of the intermediate stage of volcanic activity, as indicated by phonolitic types, trachyte, and phonolitic trachyte [28]. In addition to the documental content, the bay is characterized by its high scenic content.

At the northern extremity of the bay is Praínha, where a substantial congregation of trachytic rocks with columnar disjunction, devoid of any discernible arrangement, descend precipitously into the ocean, giving rise to the formation of intriguing topographies (Figure 8A–C). The west–east structure under scrutiny corresponds to a substantial fault, displaying iconographic content, which separates the northern part of the island, predominantly consisted of plateaus and cliffs, from the southern part, characterized by the presence of hills, valleys, and cliffs.

4.1.4. Nova Estrela Viewpoint

The Nova Estrela viewpoint, situated on Príncipe Island, provides an exceptional vista of the Boné do Jóquei (Jockey’s Cap) Islet, a rock formation displaying symbolic content [15]. From this vantage point, observers can appreciate the palm-covered rock formation and its role as a feeding ground for birds. Visitors have the option of embarking on a boat excursion to the islet, which offers an outstanding scenic view. Additionally, it has been observed that the platform in question has the capacity to display content that is conducive to esthetic appreciation. It is one of the locations in which the laterite crust is overlaid upon the most recent lava, resulting in a substantial cartographic stain. The topography of this region is characterized by a pronounced incline, leading to a precipitous descent to the coastal landscape (Figure 9).

4.1.5. Antena Viewpoint

The Antena viewpoint is an observation point located on Príncipe Island that offers panoramic views of the sea, mountains, and Praia do Macaco. It is a popular destination for tourists who wish to appreciate the region’s natural beauty (Figure 10). The most recent series is exposed in the outcroppings and is overlain, in certain locations, by lateritic crust.

This hidden gem offers a panoramic view that is simply awe-inspiring, making it a must-visit for anyone looking to immerse themselves in the region’s serene landscapes. This location is well suited for nature enthusiasts and those seeking adventure, as the surrounding area offers opportunities for hiking and exploring the local flora and fauna.

4.1.6. Banana Beach Viewpoint

Banana Beach is in the locality of Roça Belo Monte and is characterized by the presence of golden sands that delineate a contour evocative of a banana. From the elevated perspective afforded by the cliff, the outline of the beach becomes discernible, and upon descending to sea level, visitors have the opportunity to experience what is widely regarded as one of the most esthetically pleasing beaches in the country. Large basaltic rocks with striated structures, likely resulting from marine erosion, are exposed along the seashore (Figure 10 and Figure 11). These formations represent the most recent series of volcanic activity on the island, occurring approximately six million years ago. The volcanic eruptions are marked by the occurrence of basanite lava flows, leading to the creation of a notable cliff on the west coast that stretches across a considerable area of the northern section of the island [28].

4.1.7. Roça Terreiro Velho

The Roça Terreiro Velho is famous for its history because it is where the first cocoa plants were brought to Africa in 1819. Since then, cocoa has been growing in this area, and today it produces the Claudio Corallo cocoa, which is considered one of the best chocolates in the world [38]. The rocks that are exposed are part of a modern series, mostly made of basalt, which is about 6 My old [28]. This matches the concept of documented content. Also, since this place offers a nearly full 360-degree view of Príncipe Island, it displays scenic content. One of the famous rock formations that can be seen from this place is the Boné do Jóquei, or Jockey’s Cap, which fits the concept of symbolic content [18] (see Figure 12A,B).

4.2. Types and Potential Use

The geological heritage sites on the island are predominantly of the volcanic type, a consequence of the island’s volcanic origin. However, other categories of geological heritage are also identifiable, including those of stratigraphic, paleontological, sedimentological, geomorphological, hydrological, geohistorical, and tectonic nature [39] (see Figure 13).

The characteristic features of volcanic type geoheritage include columnar and spheroidal disjunctions, volcanic breccias, pillow lavas, and volcanic bombs. These features are readily observable at various geosites on the island.

The topographical features of the island, including peaks, islets, and hills, are indicative of its rugged character and contribute to its geomorphological geoheritage. The sedimentological geoheritage of the region is characterized by the presence of conglomerates, flood deposits, and volcanic sediments, as evidenced in several geosites. The geoheritage of stratigraphic type encompasses geosites where the lithostratigraphic boundaries between the island stratigraphic units are particularly well exposed.

A comprehensive evaluation of the geosites on the island of São Tomé reveals that landscape features predominate over other forms of geoheritage, underscoring the island’s remarkable esthetic appeal and its significant potential for geotourism and education (Figure 14). Conversely, the educational of the geosites is equally pronounced, while their scientific potential is constrained to geosites that are relevant to the island’s geographical location in the CVL, or that facilitate the narration of notable episodes in the island’s geological history. However, this perception necessitates specialized knowledge of geological phenomena.

To ensure that the public comprehends the geological processes that resulted in the formation of the island, it is imperative to interpret the meanings exhibited by the geological heritage sites previously described. This understanding should act as the basis for creating a geo-itinerary, which seeks to clarify the island’s geological history. This initiative is further bolstered by the implementation of suitable digital interpretative tools, given the sufficient internet coverage in the country. The organization and description of geological heritage sites must be conducted in a manner that utilizes meaningful messages, that is, within the context of simplifying geoscientific discourse to facilitate understanding among the public (“storytelling”), as opposed to focusing on experts in the field of geosciences [15].

5. Discussion

The present study focuses on the geological heritage of Príncipe Island, which is considered to be one of the world’s most significant biodiversity hotspots. The hypothesis advanced here is that this distinction can be attributed to the island’s location within the CVL and its notable geodiversity.

Despite their social dimension, western approaches to geoconservation should not be applied without the necessary and precise adaptations to the African context [40] due to the cultural, political, and socio-economic issues and histories between Africa and Europe [41]. The present study focuses on a limited geographical area with a relatively small number of geosites, where a quantitative assessment may not be the most appropriate approach [42].

This is a critical factor to consider when discussing the geological heritage of territories with markedly disparate dimensions, such as Mauritius [43], Sao Tome, and Principe ([13] and references therein).

Traditional approaches to geoheritage assessment are quantitative in nature [1,4,42]. Most of them were designed for Euro-Asian territories, where geological knowledge is quite developed. The concept of “scientific value” is dominant as the key to distinguish between geosite/geoheritage element from geodiversity site/element [42]. However, when dealing with African territories, some variables used in such approaches are meaningless. Moreover, some geosites are preserved and even valuated for non-scientific reasons; therefore, such sites cannot be geoconserved without considering geoheritage. As pointed out by [44], “effective protection of geological objects displaying heritage value requires the local community’s involvement in all geoconservation actions, i.e., inventory, evaluation, conservation, valuation and monitoring procedures, and not only at the final part of the process, when it is expected from local communities that the physical integrity of such objects is guaranteed”, as such, “both social and scientific components must be taken into account in geoheritage evaluation procedures”.

Conventional methods of geological heritage assessment are quantitative in nature and have been influenced by European and Asian practices, where a robust foundation in geosciences is well established. In African territories, however, the reality is different, and it is necessary to resort to empirical, social knowledge in the assessment of geological heritage, since geoconservation is not limited to procedures for inventorying geological heritage; it is fulfilled when the assessment, conservation, enhancement, and monitoring of geological heritage (empirical or science-based) are carried out. The qualitative assessment system utilized within the Sao Tome and Principe framework facilitates the integration of scientific and empirical knowledge, a methodology that can be widely adopted across most African territories, which are home to a significant portion of the Earth’s geological heritage.

A number of these geological heritage sites are part of the Biosphere Trail, which is part of the UNESCO Biosphere Reserve. However, the Biosphere Trail places emphasis on the biotic components of the island, while neglecting to address the abiotic elements. In light of the pivotal function of geodiversity in this region, it was feasible to ascertain the influence of geodiversity on these pathways. The routes provide an opportunity for the identification of geological heritage sites that serve as ideal habitats for species endemic to Príncipe Island.

Subsequent efforts will involve incorporating the values outlined in this study into the biosphere trail, thus articulating a theme that explores the intersection of geological heritage and local biotic and cultural values [33].

6. Conclusions

The geological heritage of Príncipe Island is exemplified by ten geological heritage sites, as well as five viewpoints that have been identified through an exhaustive inventory and qualitative assessment of their geodiversity. These sites form the foundation for a comprehensive narrative that elucidates the island’s geohistory.

The objective of this study is to raise awareness of the potential inherent in the geological heritage sites inventoried and to facilitate their publicity in areas where the biotic component is protected and highly publicized. It is imperative to emphasize the role of the abiotic component in this context, as well as to demonstrate how its preservation enables healthier habitats for the island’s fauna and flora to be established. The geological heritage of Príncipe is intricately intertwined with the island’s biodiversity, underscoring the interconnected nature of ecological and geological processes, which provide a comprehensive view of the island’s historical growth and evolution.

Príncipe geological heritage sites were inventoried and assessed using the same qualitative methodology previously applied to the geological heritage of São Tomé Island, therefore making it possible to complete the country’s national inventory of geological sites, as well as to enrich the representation of African geoheritage among the world’s list of geological heritage sites.

This work contributes to the establishment of the island’s geological heritage by offering approaches to the public in the fields of geotourism, geoconservation, and geo-education in a territory with high potential for ecological tourism. The work also has the potential to be valued in terms of scientific tourism in both directions, i.e., bioconservation and geoconservation. This approach would contribute to the conservation of the territory’s natural values.